Portrait of the artist as a scrofulous gargoyle

Damned to Fame: The Life of Samuel Beckett by James Knowlson, Bloomsbury, pounds 25

As a child it was Samuel Beckett's habit to fling himself out of trees. He would climb to the top of a 60-foot fir and launch himself at the ground, relying on the lower branches to break his fall, and clambering back up until stopped by his long-suffering mother. James Knowlson's biography reveals that the grown-up Beckett was also obsessively keen on perilous diving, in swimming pools, off cliffs, in dreams. It is piquant to consider Beckett, the most hermetic figure of 20th-century literature, as a kind of prototypical bungee jumper.

But one of the joys of Knowlson's biography is to present a whole gallery of Becketts we never knew. There's Beckett the best man, for instance, at his friend Geoffrey Thompson's wedding in 1935 (he thought it would be a registry office job and was horrified to discover a full church social was planned.) There's Beckett the actor, arriving on the Trinity College stage in a long white Father Time beard in George Pelorson's Le Kid; Beckett the roller-skater (he was so inept, the management thought he was drunk and threw him out); Beckett the Arcadian piper, tweetling on a rusty tin whistle in Paris; Beckett the artist's model, embarrassedly posing for "a lot of bloody virgin squaws" in Hamburg; Beckett the aspirant film director, writing to Sergei Eisenstein asking for a job at Moscow's State Institute of Cinematography.

And there's Beckett the ladies' man. Though far from an obvious Romeo - catatonically shy, mortifyingly silent, - he managed to draw to his angular side an extraordinary number of high-spirited and independent women with whom he would fall hopelessly in love, spend unconscionable hours agonising about whether to have sex with them, and leave them bewildered. He usually spelt disaster: Joyce's daughter Lucia fell in love with him and, when politely rejected, went mad; his sexy cousin Peggy died of consumption; his favourite co-student, Ethna MacCarthy, nearly died when Beckett crashed his car into a bridge. An obsessed Peggy Guggenheim wrote ominously in her diary, "I love being with him. It is more and more my real life. I have decided now to give up everything else even sex if necessary and concentrate on him". It's characteristic that, when he met Suzanne Deschevaux- Dumesnil, the best he could say about her was, "As we both know that it will come to an end, there is no knowing how long it may last". It lasted 50 years.

The Beckett you expect to find - solitary, tormented, epically miserable, glacially brilliant but with a curious gift for silent friendship - is here too, every move of his 85 years exhaustively documented through 850- odd pages, every allusion in his letters, every name and character and glancing reference in the prose and plays and poetry from Proust to Comment Dire. James Knowlson, the distinguished director of the Beckett Literary Archive at Reading, has been steeped in the works and in every literary-critical posture visited on the Beckett canon in the last 20 years, and presents us here with a tremendous act of elucidation and synthesis, ballasted with hitherto unseen diaries (such as those from the lost years of arty wandering in Germany in 1936-7) and underpinned by the bonus of Beckett's own plain reminiscences.

Beckett was born into a prosperous family of south Dublin Protestants, descended from Quaker land surveyors and mill owners on his mother's side and a clan of sport-fixated builders on his father's, he had a notably untraumatic childhood filled with boisterous relations, and summer holidays in a Wicklow fishing village. Beckett's mother, May, later to be his scourge and heartbreak, organised dog shows for the Parish Church of Foxrock; his father, Bill, was a bluff, non-intellectual clubman and quantity surveyor, keen on brisk walks and bridge parties. The precocious schoolboy became the cricketing super-student at Trinity, went to Paris and became an acolyte and amanuensis of James Joyce - then abruptly gave up teaching, and worked at melancholia full-time. The personality that comes off these pages is intriguing but hard to love. A taciturn and solitary child (at kids' parties, he'd hide in the outhouses), Beckett became a moody and withdrawn adolescent, an unengaged teacher, a reluctant academic, a diffident lover, an intense and brooding presence in drawing-rooms from London to Munich.

Though he underwent two years' treatment for it, he could never explain what caused the characteristic air of bitter weltschmertz that he carried from his youngest days. Knowlson points out that Beckett's sufferings weren't just psychological: his brand of depression made him unable to walk at times, while his constitution was chronically under siege from pleurisy, cysts, boils, septic fingers, night sweats and what he called a "bursting heart" (He looked, he wrote in 1930, "like a scrofulous gargoyle"). He was a walking psychopathology lab. His friend Geoffrey Thompson said that the key to understanding him was to be found in his relationship with his mother who developed into a guilt-making termagant, chronically embarrassed by her son. But it was she who subsidised his therapy sessions in Paris and chastised him for leaving his teaching post and writing filth.

His reply was to travel around Europe, soaking up the cultural movements of the Thirties with such demented acquisitiveness, one is forced to wonder if the roots of his art lay, not in transcending the various movements of post-modernity, but in something simpler. "I wish we could meet and talk," he once wrote to his friend, Tom MacGreevy, "before I become inarticulate or eloquently suave". Suavity, sociability, good manners, all held a kind of horror for him - not only because they suggested a formal bogusness, but because he was no good at them, preferring art and his own intellect.

When his brother Frank got married, Beckett complained about "the awful unconscious social cynicism that knows that what the relationship comes down to in the end is gongs and tea-trolleys"; alongside this familiar attitude-striking is the cry of an excluded soul. After an evening with German artists and Russian aristocrats, he wrote: "I am always depressed and left with a sense of worthlessness at the beautifully applied energy of these people...In comparison I am utterly alone and without purpose, alone and pathologically indolent and limp and opinionless and consternated ...This absurd diary with its list of pictures, serves no purpose, is only the act of an obsessional neurotic".

"This absurd diary" refers to the notebook he always kept, listing the names of works he'd seen in galleries. Knowlson takes these neurotic inscribings very seriously, faithfully clocking up every Caspar David Friedrich or van Ruysdael landscape seen, every book read, every performance attended. The biography's energy level falls in these cut-off years. It's as much a relief to the reader as it clearly was for Beckett when the war supervenes and, shaken by Nazi censorship of his friends' "decadent" works, he elected to join in the French war effort.

Knowlson's chapters on Beckett's war - spent, first, translating for a Resistance cell in Paris, then in nervous retreat in Roussillon, in the rural Vaucluse, with his wife-to-be Suzanne and a cast of expatriates - are the best in the book, a vivid evocation of enforced simplicity and small-town rumourings, of chess and frugal meals and chat in the Escoffier cafe in the middle of a war zone.

The heart of this biography, though, is its attempt to discover "how the arrogant, disturbed, narcissistic young man of the early 30s could possibly have evolved into someone who was noted later for his extraordinary kindness, courtesy, concern, generosity and almost saintly 'good works'." Knowlson's answer is that the war and its aftermath pulled him out of his solipsistic stupor and substituted genuine feeling for metaphysical angst. Along with this came the famous "revelation" that's half-revealed in Krapp's Last Tape: "that the dark I have always struggled to keep under is in reality my most precious ally". This rejection of Joycean light and inclusiveness in favour of Beckettian failure, impotence and ignorance was crucial: in it he found the heart of his work, namely the Trilogy (Molloy, Malone Dies, The Unnamable), and all the infinitely- pared texts and dramas that followed.

I'd quarrel with the title of this book (damned to fame? Beckett agonised about non-publication like the most coloratura prima donna; he wanted an audience, if only to counter-balance his mother's disapproval) but nothing else. Its amplitude, its oceanic research and tireless intelligence, its pacing and verve and critical acuity mark it as one of the great post- war biographies. Whatever celestial or infernal zone he currently occupies, Beckett must be permitting himself a brief, wintry smile at last.