This remarkable and controversial novel tells the story of the Holocaust and Nazism through the eyes of one of the executioners, an SS officer on the Eastern Front. Littell inserts his narrator, Max Aue, into a landscape of impressive historical exactitude; the pages describing Stalingrad are especially rich in pace and clarity and there are superb fingernail sketches of senior Nazis, including one of Hitler in his bunker. But this is also a gripping military adventure story, a study in collective pathology and, above all, a sophisticated exploration of issues of morality, evil and luck. Littell told interviewers that the character of Aue allowed him to examine what he himself might have done had he been born in different circumstances at a different time. The novel as a whole brilliantly shows how "ordinary men" become killers. Though it has its flaws - the copious scatological and sexual references may strike some readers as excessive, and the subplot is overwrought and far-fetched - Littell has undoubtedly succeeded where many ambitious writers have failed. The Kindly Ones reveals something that is desperate and depressing but profoundly important, now as ever. As Aue states with typically brutal clarity: "I am a man like other men, I am a man like you."

One approaches the fictionalisation of any aspect of the Holocaust with suspicion. Art is always at some level entertainment, and the idea of being entertained, however skilfully, by this particular set of horrors seems inherently objectionable.

Jonathan Littell's The Kindly Ones reprises the familiar atrocities, in graphic detail and at massive length, from the viewpoint of an SS officer intimately involved in their execution. The book, which has already won the Prix Goncourt (Littell grew up in Paris and wrote it in French), is certainly skilful. It's certainly objectionable too, deliberately so: the resentment and repugnance it arouses are evidently a part of its underlying calculus. One's abiding sense of something pornographic about the whole enterprise is orchestrated - cleverly, horribly - into the comprehensive disgust at one's own species that it seems intent on arousing. Despite the title (the Kindly Ones are the Eumenides, agents of catharsis in Greek drama), this is not one of those works that set out to leave you with a feeling of teary uplift about the Holocaust (a strong point in its favour).

The officer, Max Aue, a lawyer in civilian life, presents himself as a cultivated man; a Nazi by conviction rather than expedience, intellectually scrupulous, highly disciplined but also sensitive (the mass killings he observes and helps to organise sicken him to the point of repeated breakdown, even as he constantly affirms, explains and re-explains his belief in their necessity). In its coupling of high culture with demonic brutality, his character seems premised on Celan's line about the preservation of Goethe's oak tree in Buchenwald: "They build the camp, they respect the oak."

The story he tells, roughly speaking, begins with his acceptance of an assignment on the ill-fated eastern campaign, to write reports on the implementation of steadily darkening directives concerning the "Jewish question". As the early victories in the Caucasus (where the unpleasant business of butchering Jews is alleviated by enlightening opportunities to visit, say, the site of Lermontov's duel) stall in the face of Russian resistance and winter, Aue falls foul of his commanding officer, and finds himself dispatched to Stalingrad. Here, after witnessing freshly apocalyptic levels of horror, he is shot through the head, but miraculously survives, waking up back in Berlin to find Himmler pinning a medal to his chest. Following his recovery he decides, after some hesitation (by now he is afflicted by nightmares, hallucinations, constant diarrhoea and vomiting), to devote his talents to ironing out the various administrative difficulties raised by the Endlösung, the final solution. In this capacity, he becomes embroiled in a bureaucratic wrangle between Eichmann, who wants to exterminate as many Jews as possible, and Albert Speer, who wants to keep as many as possible alive to use as slave labour: one of many grotesque moral dilemmas the book explores with gloomy brilliance.

A common effect of reading histories of the Holocaust is the helpless desire for exegesis that they leave you with. The eagerness with which Hannah Arendt's line about the "banality of evil" has been seized on as holy writ is a measure of the intensity of this need. One way of looking at Littell's novel is as an attempt to use the resources of fiction to supply this missing dimension: a kind of gigantic thought-experiment whereby the reader is situated in the Nazi nightmare subjectively, via the consciousness of a living, thinking, tormentedly willing participant, whose nervous system reacts more or less humanly to the inferno surrounding him, whose mind is endowed with a conveniently encyclopedic frame of reference to help us make sense of it. He perhaps even, thanks to his head injury, possesses the legendary pineal "third eye", capable of penetrating into the spiritual essence of things.

In this respect the book rises impressively, even magnificently, to its own occasions, building out of its fact-crammed but stately sentences (the impersonal prose resembles that of a mandarin memoir) vast and phosphorescent tableaux vivants seething with Dantesque detail. If you have an interest in feeling your way into the administrative manoeuvring, the pseudo-scientific argumentation about language and race, and the mass of period-specific social and sensory minutiae that comprised the human reality out of which arose, say, the massacre at Babi Yar, or the final death march from Auschwitz; if you care to revive, in your own psyche, the finer points of cannibalism in Stalingrad or the emotional impact on the war-weary Gauleiters of Himmler's call, at Posen, for total genocide, then this is undoubtedly a book you should read.

It does, however, have some large flaws. The most serious, for me, was Littell's decision to equip his protagonist with a radically abnormal set of psycho-sexual characteristics. An erotic obsession (briefly consummated) with his twin sister Una, a murderous hatred of his mother and stepfather, and an inconsolable grief for his absconded father, form the basic elements of his inner life. Rejected by Una as a lover, he compensates by taking male lovers in order to pretend to himself that he is Una, as they penetrate him. And on a sick leave in the south of France he hacks his mother and step-father to death with an axe (he denies this, but is pursued by a pair of semi-comic furies in the form of two doggedly relentless Kripo cops, throughout the rest of the war).

These quirks establish Aue as a familiar literary type: the rococo personality who believes himself to be impeccably classical. They also fulfil the standard trope equating Nazism with extreme kinkiness. The problem is that they undermine Aue's repeated claim (one that seems to represent the basic philosophical claim of the book) that we, the readers, are no different and would have behaved just as he did under similar circumstances: "The real danger for mankind is me, is you." This Baudelairean assertion may be valid in theory, but a character who gets his kicks watching mother and stepfather eating the sausages he's just sodomised himself with seems perhaps not the most persuasive basis for a claim that we're all alike. At least Eichmann's "banality" is something most people can relate to.

What this novel offers instead is a study in the exoticism of evil. The more perverse it gets, the less representative Aue seems of anything other than himself. By the end, after extended scenes of him having sex with half the furniture in his sister's abandoned house, we're left with a pure singularity: a ghoul belonging more to the fictional universe of, say, Bret Easton Ellis's American Psycho (there's an interesting affinity between Aue's cultural name-dropping and the brand-name obsession of Ellis's Patrick Bateman) than the real-world squalor of Nazi Germany.

Related to this dubious claim of kinship is an intermittent suggestion of larger historical mirrorings. An anachronistic use of the word "terrorists" for the Maquis seems slyly aimed at current political discourse, as does the word "surge" in a remark about the floundering German war effort. And several scenes of soldiers photographing their own atrocities inevitably recall Abu Ghraib.

All of which is interestingly provocative. More troubling is a persistent effort to establish underlying reciprocities between the Nazis and the Jews. In one of his hallucinatory moments, Aue sees Hitler metamorphosing into a rabbi. Another character, citing Disraeli's Coningsby as a proto-Nazi text with its paean to the Chosen People as "an unmixed race ... the aristocracy of nature", observes that the Jews "are our only real competitors ... Our only serious rivals". Eichmann worries that sparing the strongest Jews for slave labour will create "the strongest biological pool", and that "in 50 years everything will start all over again".

Is that intended as an oblique reference to the present? Maybe, maybe not. But this, from Aue himself as he reflects on the Warsaw uprising, surely is: "It's the Jews who are becoming warriors again, who are becoming cruel, who also are becoming killers. I find that very beautiful." It's difficult to read that without thinking of certain contemporary commentators who take pleasure in likening modern Israel to Nazi Germany; harder still to figure out where Littell himself stands in relation to his protagonist's sentiments. At moments like this, the authorial detachment he cultivates with such magisterial elegance seems evasive.

At one point, Aue quotes the critic Maurice Blanchot's description of Moby-Dick as a work that "presents the ironic quality of an enigma and reveals itself only by the questions it raises". I suspect this may express something of Littell's ambitions for his own monumental inquiry into evil. To say that it falls short of Melville's visionary originality (and lacks, also, the breadth and vitality of Tolstoy, despite the claims of some reviewers) is hardly a criticism. It's a rare book that even invites such comparisons, and for all its faults, for all its problematic use of history, The Kindly Ones does just that.

 James Lasdun's short story collection It's Beginning to Hurt is published by Cape in April.

This remarkable book was first published in France in 2006, as Les Bienveillantes. The first significant work of Jonathan Littell, Francophone son of American spy author Robert, it was an entirely unexpected success. Gallimard, the publisher, originally printed 5,000 copies. Within months, Les Bienveillantes had sold 300,000 copies, had been welcomed by critics as the most important book for 50 years and had won the Goncourt and Femina prizes. Stupendous sums were paid for its foreign rights and it went on to sell more than a million copies across Europe. Now it has been translated into English and will surely cause a similar fuss.

What accounts for the attention? A 900-page work written in impeccable French by an American, albeit one educated in France, was always going to be talked about. But the main reason for the book's notoriety is its subject matter. The novel tells the story of the Holocaust and Nazism through the eyes of one of the executioners, an SS Obersturmbannfürher on the Eastern Front who is attached to the Einsatzgruppen, the mobile execution squads whose task it was to kill Jews, partisans and other "undesirables" in the wake of the German advance. Both in France and across Europe, there were fierce debates about the morality and feasibility of giving voice to such a character. In Germany, Littell was accused of being "a pornographer of violence".

But The Kindly Ones also owes its success to its quality as a work of fiction. Notwithstanding the controversial subject matter, this is an extraordinarily powerful novel that leads the stunned reader through extremes of both realism and surrealism on an exhausting journey through some of the darkest recesses of European history.

Max Aue, the narrator, is a jurist by trade, a classicist by training and an aesthete by nature. He reads Flaubert as he treks through northern Pomeranian forests escaping oncoming Russian forces and savours the finest claret. (As German critics pointed out, Littell is more at home with French cultural references than German ones.) Aue is interested in the potential philosophical justifications for the mass murder of Jews and regularly consults Plato. At the same time, he is a closet homosexual who once had an incestuous affair with his sister and is a suspect for the brutal murder of his mother and stepfather. Whether all these elements add up to a plausible character (or even a plausible Nazi) is debatable. But as Littell has stated, with his interest in Greek philosophy and his cold, ironic eye, Aue is an excellent prism through which historical events can be examined.

One of Littell's purposes with this novel is clearly a documentary one. Whatever other criticisms have been levelled at it, no one has questioned the thoroughness of his research, an exhaustive process that took five years and included walking the terrain he describes. (The book was written quickly, by hand, one winter in Moscow.) Littell inserts the character of Aue into a landscape of impressive historical exactitude; the pages describing his arrival in Stalingrad are especially rich in detail, pace and clarity. This is narrative photo-realism, the work of a gifted writer who in lean, sharp prose conjures a powerful sense of place and action. His fingernail sketches of senior Nazis, including one of Hitler in his bunker, are superb. No wonder French critics hailed the return of 19th-century realism and even spoke of a new War and Peace.

Yet it would be wrong to value The Kindly Ones only for its contribution to history. The novel is also a gripping military adventure story and a study in collective pathology. Above all, it is a sophisticated exploration of issues of morality, evil and luck. Littell told interviewers that the character of Aue allowed him to examine what he himself might have done had he been born in different circumstances at a different time. In the preface, Aue assumes a creepy complicity between himself and his readers. His opening sentence - "O my human brothers, let me tell you how it happened" - recalls, especially in the French original, Charles Baudelaire's: "Hypocrite lecteur, mon semblable, mon frère." Littell's point is that there is no firm line separating ordinary people from those responsible for acts such as the Holocaust. There is no absolute evil, banal or otherwise. There are, as Aue says, simply "reasons, good or bad ... human reasons".

The novel as a whole brilliantly shows how "ordinary men" become killers. Through its first 200 pages, we follow an Einsatzgruppen about its grisly work. Though many of its members are vicious antisemites and sadists, most are distinctly normal. As massacre follows massacre, they are progressively brutalised. At first, some balk at shooting unarmed civilians, but soon such reluctance becomes a thing of the past. The men eat sausages and drink beer in pauses during the "Aktion" at Kiev, which saw more than 30,000 Jews killed in two days. Their commanders have difficulties holding back volunteer shooters. By the time Aue arrives at Auschwitz, this process of collective desensitisation has reached a new extreme. Industrialised death on a vast scale, conceived in part to spare troops direct involvement in mass killing, is seen as a rational, indeed inevitable, solution to "the Jewish Problem".

This view of Nazi actions is certainly in keeping with the latest Holocaust scholarship, which has destroyed the "I had no choice but to follow orders" excuse. Recent work has shown that those rare individuals who refused execution squad duty were not punished. The truth is that though many found shooting unarmed Jews, especially women and children, highly disagreeable, there was no great desire to step out of line. An unswerving belief in the necessity of their task meant that initial qualms were overcome and they came to see killing as a job like any other.

The Kindly Ones, unsurprisingly for such an ambitious novel, does have flaws. The copious scatological and sexual references may strike some readers as excessive. From the lengthy descriptions of Aue's diarrhoea to the dying slave workers in the Reich's factories who shit standing up because to stop working would mean certain death, this is a novel preoccupied with faecal matter. At one point, Max, living his own Armageddon as Germany collapses around him, sodomises himself with a tree branch.

Likewise, the incestuous and murderous subplot, that sees Aue pursued across half of Europe and half the 900 pages by two police officers, is overwrought and far-fetched. Littell often allows his narrative to ramble, devoting 60 pages to an impossibly bureaucratic argument between the SS and the regular army over the precise definition of Jews in the Caucasus, and other long passages to turf wars between senior Nazis. These sections make important historical points, but readers may struggle to get through them.

Having read the novel in French on its publication, I also found the translation overly literal. Aue's words seem much more foreign, stilted and sententious than they did in the original. Littell chose to write in French because it best renders Aue's mix of viciousness, chilly irony and confidentiality. In that language, he is precise, ironic, almost intellectually playful and certainly provocative. In English, at least in this translation, he often comes across as precious.

Littell's final message is naturally bleak. Our relative relegation of this greatest of European traumas to memorial days, museums and books is a useful way to avoid confronting the most difficult questions of all, which are not about the victims, but about the killers. Any attempt to portray the perpetrators of the Holocaust as human, such as the recent film of Bernard Schlink's book The Reader, provokes massive controversy. It will thus be interesting to see how this book is received in the English-speaking world.

Whatever reaction his novel sparks, Littell has undoubtedly succeeded where many ambitious writers have failed. The Kindly Ones reveals something that is desperate and depressing but profoundly important, now as ever. Max Aue, the SS executioner, states the truth with typically brutal clarity: "I am a man like other men, I am a man like you."

 Jason Burke is a senior foreign correspondent at the Observer based in Paris.