A fine murder story is like a great love affair: an infinite catacomb of excitement, sorrow and desire. Apart from tales of love and death, what else matters to mankind's stone-age brain? While we continue to push back the frontiers of knowledge, most recently in digital technology, our consciousness remains hard-wired with some very primitive storylines. The lasting challenge to literature is to achieve a satisfying marriage between high art and the low drives of a simple plot. The latter is usually much more demanding than the former. To find such a rapprochement in the pages of a novel is indeed a rare treat.

This is where Javier Marías, one of Spain's greatest contemporary writers, steps into the picture. The son of a victim of Franco's dictatorship, Marías is a characteristically European version of the literary man. He works as a distinguished translator, has a column in El País, and runs his own publishing house. He is also the author of two short story collections and 13 novels whose lyrical, conversational, and even errant, style has sponsored widespread literary admiration. There's an irony here because, rather appealingly, Marías writes fiction as if there were many other, better things to do. At his investiture into the Royal Spanish Academy in 2008, he confessed that the work of the novelist was "pretty childish", a teasing line of thought derived from Robert Louis Stevenson. His other exemplars are Joseph Conrad and Laurence Sterne. So it's no accident that he went on to argue that the writer "can only tell stories about what has never happened, the invented and the imagined".

The Infatuations is just such a novel, a murder story of archetypal simplicity whose slow unravelling becomes a vehicle for all the big questions about life, love and death. There are passages on almost every page that cry out for quotation. This may be a literary and metaphysical fiction, but it's never boring. Marías plays with perception, memory and guilt like a toreador. With every flourish of his literary cape, the enthralled reader is never allowed to forget that, in the end, the author will make a killing. Just as Macbeth is a thriller that's also a great tragedy, The Infatuations is a murder story that's also a profound study of fatal obsession.

A story that might have been torn from a crumpled page of Home News starts with el enamoramiento, a Spanish term for which there is no English equivalent  the state of falling or being in love, or perhaps infatuation. María Dolz, a publisher's editor, has become fascinated by the glamorous couple she sees every day in the cafe where she takes breakfast on her way to work. "The nicest thing about them," says María, "was seeing how much they enjoyed each other's company." Then, one day, they are no longer there, and María feels lost without them. Later, when she sees a newspaper photograph of the husband, lying stabbed in the street, she begins to learn more about this mysterious couple and to uncover their story.

She becomes infatuated by the infatuees. When her own romantic life, brilliantly imagined by Marías, links her to the murdered man's widow, Luisa, an apparently random killing becomes, inexorably, a much darker tale of calculated homicide. In the process, María the narrator becomes an unwitting accomplice to a dreadful crime, a young woman trapped in a prison of guilt. "No one is going to judge me," she says at the end with a doomed insouciance, "there are no witnesses to my thoughts." It's a terrifying conclusion to a haunting masterpiece of chilling exposition.

The Infatuations has already been showered with awards and acclaim. With this exemplary translation, Penguin adds a European master to its distinguished list of contemporary international fiction. Great Spanish novels don't come along too often, but they sometimes find a place in the hearts of the British reading public. The full text of Don Quixote was first published as long ago as 1620. I wouldn't be surprised if The Infatuations soon acquired an equally devoted following.

The strict sequence of events that makes up our lives seems to us, as it takes place, haphazard. A chance encounter, a sudden death, love at first sight, an overheard conversation, all belong, we imagine, not to a tightly plotted thriller but to the erratic jottings of a distracted dreamer. A woman might notice a couple meeting every day in the same cafe, discover later that the man has been stabbed to death by a demented beggar, and decide to speak to the widow the next time she sees her. Each of these events seems whimsical and arbitrary and yet, as Javier Marías shows in this masterly novel, chance is nothing but the result of our own negligent reading. Read in the proper order, from the first to the last chapter, everything we do and everything we witness, however unlikely or disconnected, fits into a story in which we are both narrators and protagonists.

Such is the case of María Dolz, a middle-aged woman who works for a Madrid publisher, who witnesses the couple's meetings, and then their absence; who discovers in the papers the murder of the husband, a certain Miguel Desverne; and who seeks out the widow, Luisa Alday, to offer her condolences. As it happens, Dolz meets Alday's new companion, a handsome man called Díaz Varela, who was Desverne's best friend. Dolz becomes infatuated with Díaz Varela and, shortly afterwards, they begin an intermittent sexual relationship.

"Infatuations" is the only possible English translation for the "enamoramientos" of the original title. Margaret Jull Costa, with her habitual skill, has rendered Marías's precise, somewhat laconic Spanish into graceful and equally laconic English, but the title necessarily defeats her. "Enamoramiento" is the act of falling in love, briefly but not less passionately; "infatuation" (the dictionary tells us) is to become inspired with intense fondness, admiration, even folly; unfortunately, in the English term, love is absent. As Dolz's lovely last words have it, after the end of an "enamoramiento" we continue to sense the loved one's presence, "knowing that he is still on our horizon, from which he has not entirely vanished, and that we cannot see, in the distance, the dust from his fleeting feet".

Dolz's narrative is studded with questions: What is her new lover's involvement with the widow? What are his true feelings towards both women? Did he have a hand in the husband's murder? And above all, what is her own role in the convoluted plot into which she seems to have fallen? Who, in fact, is she?

The classical themes of love, death and fate are explored with elegant intelligence by Marías in what is perhaps his best novel so far. The story's literary underpinnings are Macbeth (as is usual in Marías), Balzac's Colonel Chabert and, more surprisingly, Dumas's The Three Musketeers, all glossed by Díaz Varela, who paternalistically instructs Dolz on the importance these three books have for him. Central to Marías's novel is Balzac's colonel, a man supposed dead who returns among the living, much like the dead Desverne returns to haunt the minds of the survivors. Over this literary chorus echoes a grisly observation quoted by Díaz Varela from the Musketeer saga: "A murder, nothing more." For Dolz, the banality of murder implied in Dumas's words becomes translated as murder's monstrous immutability. "A thief can give back the thing he stole, a slanderer can acknowledge his calumny," Dolz thinks to herself. "The trouble with murder is that it's always too late and you cannot restore to the world the person you killed." She adds: "And if, as they say, there is no forgiveness, then, whenever necessary, you must continue along the road taken." Except that, eventually, the murderer will no longer think of his crime "as a monstrous exception or a tragic mistake, but, rather, as another resource that life offers to the boldest and toughest." He will feel as if he has simply inherited the terrible action, or won it at a raffle "from which no one is exempt". And this feeling will lead him to believe "that he didn't wholly commit those acts, or not at least alone". In these extraordinary words, Marías has defined the ethos of our time.

Marías is an old hand at hoodwinking the reader, layering his novels with plots that seem, each one, final, but then suddenly blossom into something unexpected. In The Infatuations, Marías may have been thinking of Macbeth's address to the witches: "If you can look into the seeds of time,/ And say which grain will grow and which will not,/ Speak then to me." Neither the reader nor the protagonists are capable of such foresight, but the clear knowledge that every event, however minuscule, might develop into a sprawling web of roots and branches, lends every detail in the novel (as it does in detective fiction) a possibly dangerous meaning. Over the events in the The Infatuations, this other, untold and latent story casts an ominous and uneasy shadow.

"Once you've finished a novel," says Díaz Varela to Dolz, "what happened in it is of little importance and soon forgotten. What matters are the possibilities and ideas that the novel's imaginary plot communicates to us and infuses us with, a plot that we recall far more vividly than real events and to which we pay far more attention."