TS Eliot has often been accused of giving poetry a bad name.

Of all the people at whom a reproving finger might be pointed, Eliot deserves better. In part, however, he only had himself to blame. The notes he wrote for the 'The Waste Land', his most famous poem, drew attention to the sources he had drawn upon and his own eclectic and arcane reading matter. Thus from the outset, it seemed, one needed to be immersed in foreign and classical literature, philosophy and folklore, to be able fully to understand what the poet was trying to say.

It was as if Eliot was setting his readers a challenge, the like of which would have had Bletchley Park's decoders scratching their heads in frustration. Thereafter, he was perceived as 'difficult', incomprehensible, wilfully obscure, more trouble than he was worth, possibly even a crackpot. This we now know, of course, was not the case. His early verse, for example, which was written in his mid-twenties, was wonderfully lyrical, deeply sensuous and enduringly evocative. "In the room the women come and go/Talking of Michelangelo," he wrote in 'The Love Song of J.Alfred Prufrock', lines that might strike us today as archetypically Dylanesque - by which we don't mean the Welsh bard.

'Prufrock' is the first poem to appear in Eliot's Collected Poems. As Robert Crawford notes in Young Eliot: From St Louis to The Waste Land, this modernist landmark - "one of the bravest poems about gender ever authored" - made little impact on its first appearance in 1915 in Poetry, a Chicago-based magazine. Its editor, remarks Crawford, stuck it at the back because "he did not greatly care for it".

At that time, Eliot was in Britain and newly married to his first wife, Vivien. From the outset, the union was fraught. Both Vivien and Tom, as Crawford addresses his subject, were caught on the rebound. Back in the US, Eliot's family was not amused but faced with a fait accompli could do nothing but gripe. Their son, desperate to lose his virginity, had got into bed, literally, with a flighty woman who was often ill, neurotic, and, almost immediately, unfaithful with Bertrand Russell.

It is a story reeking of melodrama which was to have a far-reaching and baleful impact on the couple. Nearly half a century later, Eliot wrote in a letter: "I think that all I wanted of Vivienne [his spelling] was a flirtation or a mild affair: I was too shy and unpractised to achieve either with anybody. I believe that I came to persuade myself that I was in love with her simply because I wanted to burn my boats and commit myself to stay in England. And she persuaded herself (also under the influence of [Ezra] Pound) that she would save the poet by keeping him in England."

Many years later, Eliot conceded that the marriage brought Vivien no happiness. What it brought him, however, was "the state of mind out of which came The Waste Land": "April is the cruellest month, breeding/Lilacs out of the dead land, mixing/Memory and desire, stirring/Dull roots with spring rain." If it's true that happiness writes white then, if nothing else, Eliot's miserable marriage provided him with the wherewithal to produce a poem that continues to hold new generations under its spell.

Not the least of this biography's virtues is its sympathetic tone. By calling Eliot 'Tom', rather than by his surname or his familiar initials, Crawford brings him into clearer, more vulnerable and more approachable focus. He is a man of his times, struggling - despite considerable family wealth, privileged education and formidable intellect - to find his path through the thicket of post-Edwardian convention.

Unlike previous biographers, who have tended to race through Eliot's formative years, Crawford places proper stress on them. Whereas Peter Ackroyd, for instance, in his book gave just 15 pages to the youthful Eliot, Crawford devotes nearly 70. He has been helped in no small measure by the Eliot estate's relaxation of access to and quotation from his papers and the recent publication of his collected letters. This, says Crawford with justification, has allowed him to write "a more accurate and intimate account" of his subject's upbringing which, in turn, was to have a profound influence on his work.

St Louis, where he was born in 1888, is recreated as a city of sounds and danger, where there was a strict divide between black and white, and Jews were regarded with suspicion if not contempt. When Eliot was born, both his parents were 45. The household was idealistic, bookish, religious, "where knowledge of saints and martyrdoms was readily taken for granted, even when it came to the punchlines of old jokes". In a city that was thriving, the Eliots lived in some style. His father, who came of Union stock, was a prominent businessman, eventually becoming a senior figure in a local brick company. When not campaigning on behalf of children, his mother was passionate about poetry, religion and philosophy, which her son, her sixth child, came to share.

Eliot was a shy boy, and prone to illness, who eschewed sport in favour of books. He was not generally liked and wasn't much of a team player but neither was he was a remarkable scholar. But he always wrote and read poetry. St Louis, meanwhile, was the locus in 1896 of an apocalyptic tornado which, while leaving the Eliots unscathed, gave the poet firsthand experience of what a waste land could look like.

Crawford, who is himself a poet and has written a well-received biography of Robert Burns, is particularly adept at demonstrating where Eliot may have sourced material for his poetry. The aforementioned Prufrock is one such; it was the name of a St Louis "manufacturer of parlor furniture". There is also a "Dr Sweany", a kind of snake oil salesman, who featured regularly in newspaper ads and who may have been the inspiration for his unfinished dramatic poem, 'Sweeney Agonistes'.

This is not to suggest that having such information is necessary to illuminate the poems but it does demonstrate their rootedness in a world that is as real as it is imaginary. In common with his equally innovative contemporaries, Picasso and Stravinsky, Joyce and Woolf, Eliot ushered in an era in which readers, listeners and viewers could not be regarded simply as passive consumers. To fully appreciate these artists' work an effort had to be made and meaning teased from the apparently meaningless. In a few short and hectic decades culture was revolutionized and calibrated anew.

Crawford's superb biography, of which this is the first of two volumes, must now be regarded as the standard work. It does not diminish or tarnish Eliot's reputation. On the contrary, it makes one want to return to the poems and read them again and again. It ends with the publication in 1922 of 'The Waste Land', in which Pound had a significant input. Rightly, Eliot thought it his greatest achievement, comparable to Ulysses. Nevertheless, he felt "about ready to chuck up literature altogether and retire".

The poem made its first appearance in print in Criterion, a magazine edited by Eliot himself who awaited anxiously the reaction to it. His own verdict, delivered a decade after the dust had settled, was withering: "To me it was only the relief of a personal and wholly insignificant grouse against life; it is just a piece of rhythmical grumbling."

Young Eliot: From St Louis To The Waste Land by Robert Crawford is published by Jonathan Cape, priced £25