In his wartime essay "England Your England", George Orwell characterised the English as a nation of hobbyists. It was the English tendency to form stamp collecting societies and angling clubs, Orwell claimed, which both cemented them as a people  giving them the cohesion to resist Hitler  and saved them from the destructive political passions that had ripped the rest of Europe apart. And, Orwell might have added, the private passion that most consumed the ruling caste in the early 20th century was the need to climb.

If it didn't exactly invent the sport of mountaineering, the English elite certainly popularised it. Sir Leslie Stephen, for example, the impeccably intellectual editor of the Dictionary of National Biography and father of Virginia Woolf, was an early president of the Alpine Club and wrote Peaks, Passes and Glaciers alongside The Science of Ethics. After England's Edward Whymper became the first man to ascend the Matterhorn in 1865, climbing became less of a casual pastime for the leisured class, and more of a national obsession. This despite four members of Whymper's party having plunged to their deaths as they descended the sheer Swiss slope.

Indeed, suggests Wade Davis in this engrossing book, it was the constant danger of sudden death that gave climbing its piquancy. Having painted one-quarter of the world imperial red by the end of the 19th century, the Edwardian adventurer looking for his next expansive frontier was obliged to look upwards rather than outwards. The average climber's career was a three-act drama, beginning on the nursery slopes of Snowdonia; progressing to the snowy peaks of the Alps, and finally  but only for the seriously dedicated  expanding to the vast and deadly ranges of the Himalayas.

This pattern endured until the world's highest mountain, Everest, was finally conquered by the Hunt-Hillary expedition of 1953. That expedition's initial meetings ended climbing's golden age, epitomised by the Golden Boy around whom Wade Davis spins his story: George Mallory. Refreshingly, however, Davis ranges far beyond the probably unanswerable question always asked of this most iconic of climbers: did he, or did he not, make it to the summit of Everest before falling to his death on the mountain in 1924, 30 years before Hillary and Tenzing Norgay "knocked the bastard off".

The discovery of Mallory's sun-bleached but perfectly preserved body in 1999, and the continuing quest for his companion Sandy Irvine's corpse (another expedition is hunting for it even now) shows that this hoary old climbing chesnut, unlike its subjects, still has life left in it. It is, though, academic: for a successful climb, mountaineers must return in one piece as well as ascend their summits. Davis digs deeper, not only into Mallory's motives, but also into the collective impulse that drove his expedition comrades  already bonded by public school, university, army, empire and a hint of homoeroticism  to risk their necks along with him. Davis finally finds the answer in the bloodiest bonding of all: the first world war.

Mallory, so the celebrated story goes, told a New York Times journalist who asked why he kept trying to climb Everest "Because it's there". This throwaway line  words that he might not have actually spoken  has been elevated into the nutshell philosophy of climbing. But Davis doesn't believe it. The real impetus behind these men's obsession, he finds, was not a macho need to prove themselves, still less a jingoistic push to plant the union flag atop the unsullied mountaintops, but an aching sense of loss. As he tells the story of the 26 men  and it must be said that this is a very male tale  who made the three assaults on Everest culminating in Mallory's last climb, Davis repeatedly traces the root of their endeavours to the horror of the trenches.

Most of them had been through the worst of the war. Six had been seriously wounded. Three as army doctors had coped as best they could with unimaginably grotesque injuries. Two had nearly died of disease. Two more had lost their brothers. One had gone through the trauma of "shell shock", and all had been marked and seared, suffering from the guilt of surviving a catastrophe that had consumed their generation, their class and their country.

Before reaching the great gulf that 1914 had carved across their lives  the crevasse opening beneath all their feet  it had been possible to view the Himalayas as just the ultimate climbing test. But after the angel of death had fluttered so close, it took on a mystical significance. Davis, himself an anthropologist and explorer with a reverence for global cultures, believes this had much to do with the influence of the fatalistic Buddhism of Tibet  the fabled, enigmatic land from which they mounted their expeditions.

Davis cites the example of Mallory's mentor, Sir Francis Younghusband. This was the soldier who forcibly opened up Tibet to the outside world in his 1904 expedition, "smashing" and killing hundreds of those he called "selfish, ferocious, filthy lecherous lamas" in the process. Inside Tibet, however, the crusty imperialist had a transcendent vision of the mystic, perceiving the unity behind all creation. Similarly, Davis sees the quest to climb Everest beginning in a national need to atone for Scott's failure to reach the south pole ahead of the impudent Norwegians, but ending in something altogether more meaningful than that.

Not everyone will be able to accompany Davis to the summits of his farreaching conclusions about the redemptive, quasi-religious powers of the world's highest mountain and the people beneath it. The oxygen there may be too thin to sustain his central argument. What is indisputable, however, is that this is a superb book. At once a group biography of remarkable characters snatched from oblivion, an instant classic of mountaineering literature, a study in imperial decline and an epic of exploration.

Nigel Jones's Tower: An Epic History of the Tower of London is published by Hutchinson.

The death in 1912 of Captain Scott and his companions in the Antarctic set a precedent of sacrifice for the generation of young British men who, a few years later, would hurl themselves into the maelstrom of the Great War. That Scott's expedition was, according to later accounts, doomed by incompetent leadership only makes its failure seem more prophetic. Now, in Wade Davis's magnificent new book, the remaining goal of imperial exploration is seen as an outcome of  and response to  the first world war. While Scott's expedition was, in some ways, an exercise in heroic futility, the conquest of Mount Everest could help to exorcise the massed ghosts of the dead.

Three British expeditions set out for Everest between 1921 and 1924, involving a total of 23 climbers, all but six of whom had seen action in the war, either as combatants or medics. Charles Bruce, for example, survived Gallipoli in spite of being "cut down with machine-gun fire that nearly severed both of his legs". Advised by the medical board "to retire to a quiet life and to be especially careful never to walk strenuously uphill", he went on to lead the second and third Everest expeditions. George Mallory, who would die on Everest in the third of three successive trips to the Himalayas, served as an artillery officer but had the good fortune of being sent home from the Somme (due to the recurrence of an old climbing injury) and missing Passchendaele thanks to a motorbike accident on a training course.

It seems likely that, having given a vivid account of the war, Davis will move rapidly on to the planning and execution of the Everest assaults. He does, but whenever new characters are introduced  there is a constant change of personnel over the course of the three expeditions  Davis details their individual experiences in battle so that the war exists not as backdrop but as a recurring series of flashbacks. Its legacy dogs the climbers along every step of their "mimic campaign", through overlapping vocabulary (in the laconic idiom of the age, expeditions and battles are both "shows"), equipment used (altitude necessitates the use of oxygen to prevent the climbers  some of whom had survived gas attacks on the western front  being "suffocated as if by some subtle, invisible, odourless gas") and, of course, by the constant threat of death.

With these expeditions Davis is on tried and tested narrative routes, guaranteed to keep the reader roped closely to the page. Extreme weather and altitude throw up phenomena that are doubly intolerable ("your feet can be suffering from frostbite," Charles Howard-Bury observed uncomplainingly, "while you are getting sunstroke at the same time") and supernaturally weird: at 23,000 feet on the first expedition, Mallory and climbing partner Edward Wheeler "began to glow with a frigid halo, an 'aureole of spindrift' and whirling snow"). Looking, in George Bernard Shaw's words, as if they were part of a "Connemara picnic surprised by a snowstorm", the team members met these and other challenges phlegmatically. (How else to react when the cold causes one to cough up the mucus membrane of one's larynx?)

Gripping stuff, obviously, but Davis  who currently enjoys the oxymoronic position of National Geographic's explorer-in-residence  is less interested in yarns for their own sake than the way they are made and hold together. In the early 1980s, the young Davis went to Haiti to investigate zombies. Having discovered the combination of drugs needed to kill people off and bring them back from the seeming dead (puffer fish poison followed by a whopping blast of datura), he then had the good fortune to meet a zombie. A scoop, by any standards, but in The Serpent and the Rainbow (1985) Davis also weaves together the history of Haitian and voodoo culture that turns belief  in zombies  into reality. Something similar can be seen operating in the book that serves as a more obvious precursor to the present blockbuster, One River (1996), in which Davis follows his mentor, botanist Richard Schultes, into the literal and shamanic wilds of the Amazon.

Into the Silence offers a meticulous recreation of how the idea of climbing the mountain grows out of the Great Trigonometric Survey of India (which leads to the naming of Everest and establishes that it is indeed the highest point on earth); the full diplomatic and political wranglings necessary even to make a start; and the immense logistical demands of such attempts once they are under way: third time around, the supplies include "60 tins of quail in foie gras and 48 bottles of champagne, Montebello 1915".

Still more impressive is the way Davis depicts the meeting of incompatible belief systems. While the British see the mountain as an obstacle to be overcome (by sheer force of Britishness if necessary), the opinion of their Tibetan hosts  that the spirits of the mountain, if not sufficiently appeased, will hurl them from its side  comes to seem just as plausible. It would be a mistake, however, to see one outlook as "spiritual" and the other as pragmatic. The Tibetans, quite reasonably, can't see any point in climbing the mountain; the British, in turn, are animated by a "mystic patriotism" that is itself a kind of delirium.

And while expedition members are delighted to see exotic wild birds that are utterly tame (due to the Lama's decree that they are sacred and not to be harmed), Tibet makes a less favourable impression on them than it will, later, on Richard Gere. Mallory calls it "a hateful country inhabited by hateful people" while some of his team-mates endure the mumbo-jumbo to which they're subjected with undisguised contempt. Though the climbing teams admire the Tibetans' capacity to endure hardship, an avalanche that sweeps seven porters to their deaths on the second expedition is announced with the relieved words: "All whites are safe!" But here too there is complexity; a member of the expedition later writes: "Why, oh why could not one of us, Britishers, share their fate?"

The differences, moreover, do not simply divide west from east. Within the British camp some view the use of oxygen  and its great advocate, George Finch  with a mixture of suspicion and contempt. "I always knew he was a shit," snorts a team-mate on seeing the Australian-born Finch repairing his own boots. Mallory, the tragic figure at the centre of the drama, contains many of these conflicts and contradictions within himself. After a Stranger's Child-style homosexual infatuation at Cambridge, he marries, has kids, and sets up home as a schoolteacher, only to be lured back repeatedly to the mountain that will claim him. Forward-thinking enough to see that the socially inept Finch is his best possible climbing partner, he is sufficiently impressed by the porters to consider shipping one back home  where he "might inhabit part of the cellar or the outside coal shed"  as a servant. Blessed with incredible natural athleticism and stamina, he is cursed by "congenital incompetence with anything technical" and prone to forget or drop items of life-saving importance.

If Mallory and his cohorts are representatives of a bygone age, their expeditions established a template that has remained unchanged. The contemporary practice of wealthy individuals purchasing a place on Everest, familiar to readers of Jon Krakauer's Into Thin Air, "began from the inception of the dream". The combination of "exclusive marketing arrangements" and sponsorship  "Avoid worry, use Sunlight Soap and for Ever-rest"  to underwrite the enormous undertaking was also in place from the outset.

To keep this mass of material from bulging out of the narrative is an impressive feat of literary organisation and management. To that extent the book is like the expeditions themselves: every inch of progress is dependent on an enormous supply train of information. There is nothing burdensome about this for the reader; the technical data is fascinating, and Davis's prose, in spite of the weight it is obliged to bear over such an extended and difficult terrain, shows only occasional signs of buckling under the strain: "For him the war was over"; "FM Bailey was himself no slouch".

What is surprising is that in narrative terms Mallory's prediction  "I have every reason to expect the climax to be no less interesting"  proves somewhat misleading. By the time we get to the final assault on the summit, excitement has given way to grim resignation. Unprecedented though they are, the challenges of the Death Zone manifest themselves as a kind of vertiginous drudgery.

Whether Mallory and his companion Sandy Irvine died on their way to the summit or on the way down remains a matter of conjecture. Either way, their deaths embody the book's larger purpose in a way that Davis might have emphasised more strongly. The Great War resulted not only in vast numbers of men dying but in their being blown to unidentifiable bits by artillery so that they were commemorated as "The Missing". For almost 75 years, until the discovery of his body in 1999, Mallory shared this fate and became their exalted representative: a name preserved high above the nameless dead.

Geoff Dyer is the author of The Missing of the Somme