Even now, if you were to ask readers to name the 20th century’s greatest poem, at least among those written in English, the answer would almost certainly be T.S. Eliot’s “The Waste Land” (1922). “April is the cruellest month” — what college student (or taxpayer) hasn’t, at this time of year, ruefully murmured its opening words? If Eliot’s haunting melange of quotation, lugubrious reflections on life and love, and achingly beautiful word-music has any serious rival for modern poetry’s Number One spot it would probably be his own later, almost liturgical “Four Quartets” (1943). (I myself prefer it.) No doubt a few fans might even opt for the same poet’s youthful masterpiece of erotic dithering, “The Love Song of J. Alfred Prufrock” (1917): “I have heard the mermaids singing each to each./ I do not think that they will sing to me.”

While Eliot’s poems continue to be greatly loved, their author himself is another matter. As Robert Crawford notes in the introductory pages of “Young Eliot” — which tracks in enthralling, exhaustive detail the poet’s life up to the book publication of “The Waste Land” — Thomas Stearns Eliot (1888-1965) has since his death become nearly as controversial a figure as his friend Ezra Pound. He’s been labeled anti-Semitic and elitist, as well as a religious nut, an abusive husband, a cuckold and a prig. Some of these accusations are, at least partly, true: “How unpleasant to know Mr. Eliot!” as he himself once wrote. And yet the same man could be wholly admirable — generous, loyal, immensely kind.

Earlier biographies — the best is Lyndall Gordon’s — have somewhat scanted Eliot’s American childhood and youth, which is one reason why this new book is so valuable. It is magisterial in its minutiae. It covers the poet’s family life in St. Louis and his summer holidays in Gloucester, Mass., his early schooling and reading, the years at Harvard and his bittersweet love for Emily Hale, literally the girl he left behind when he moved to England. To humanize a figure often (wrongly) regarded as coldly marmoreal, Crawford calls his subject “Tom” throughout. He also promises a second volume sometime after Hale’s letters become available to scholars in 2020.

While proffering a steady flurry of names, facts and occasional trivialities, Crawford nearly always relates his discoveries to the poetry, at times quite subtly, as when he notes that Eliot’s sister Margaret was sensitive to the sound of thunder (the last section of “The Waste Land,” titled “What the Thunder Said”). In these pages, you will learn that a Mr. Prufrock owned a St. Louis furniture store and a Dr. Sweany advertised tonics to increase male energy and vigor. No possible connection to Eliot’s published work, however faint or distant, goes unnoticed.

But Crawford, who is a professor of modern Scottish literature at the University of St. Andrews, also interweaves several ongoing themes. Eliot grew up the scion of a distinguished family of preachers, educators and wealthy businessmen (his father owned a brick factory). As the youngest of six surviving children, Tom was distinctly cosseted, especially by his doting mother (who wrote poetry). The reserved, physically delicate boy — he was born with a double hernia and needed to wear a truss; children mocked his big ears — never played sports and seems to have had almost no close friends. Instead he began to scribble at an early age, producing a family magazine of his own stories and jokes: “Eat Quaker Oats” was reworked into “Eat Quaker Cats,” with a feline sketch. (Crawford expects the reader to remember that Eliot later produced the Edward Learish “Old Possum’s Book of Practical Cats,” the basis for the musical “Cats.”)

”Young Eliot: From St. Louis to The Waste Land,” by Robert Crawford. (FSG)

While Eliot always maintained that he had a happy childhood, by adolescence this sheltered Little Lord Fauntleroy existence began to chafe. His social relations — especially with girls — suffered because of his shyness and acute anxiety about his body image. Despite surprisingly mediocre grades, he was nonetheless admitted to Harvard as a kind of legacy student — and nearly flunked out as a freshman. Away from home, he loafed, frequented music halls, joined dining clubs and secret societies. The more polite of his youthful verses appeared in student publications; the ribald and offensive ones — with rhymes ending in “unt” and “ugger” — their virginal author reserved for the private delectation of frat-boy hearties he wished to impress. (All this juvenilia can now be yours in a collection titled “Inventions of the March Hare: Poems 1909-1917.”)

Eliot finally discovered his true voice when, in 1909, he happened upon the work of Jules Laforgue. Electrified by what he read of Laforgue in Arthur Symons’s “The Symbolist Movement in Literature,” the Harvard undergrad ordered the French poet’s “Oeuvres complétes” from Paris. Crawford devotes an entire chapter to what Eliot found so exciting, noting, for instance, that one of Laforgue’s lines could be translated “I will have spent my life in failing to embark.” That could be the voice of a 19th-century J. Alfred Prufrock.

By the time of his graduation, Eliot had begun his self-metamorphosis into an academic powerhouse. Following a studious year in Europe, he returned to Harvard to work toward a PhD in philosophy. Crawford notes that at this time Eliot not only read the contemporary philosopher Henri in French, but “he also read Patanjali in the original Pali, the ‘Upanishads’ in Sanskrit, Heraclitus in Greek, Kant in German, Dante in Italian” and Spinoza in Latin.When awarded a traveling fellowship, the youthful polymath headed for Oxford.

At this point, Crawford enters more familiar biographical territory. Still, he is superb in describing Eliot’s life in England, why the young scholar and the vivacious but fragile Vivien Haigh-Wood married so impulsively in 1915 (he was hungry for sexual experience, she was on the rebound from his friend Scofield Thayer) and how the awful daring of that moment’s surrender — “Which an age of prudence can never retract” — played out sadly for them both over the next several years.

Needing money for his new life, Eliot landed a steady job in a London bank, while also launching a career as a lecturer, editor and reviewer. (His best literary journalism was repurposed for his epochal 1920 volume of criticism, “The Sacred Wood.”) At the same time, the couple’s heady social life brought them into the orbit of the philosopher Bertrand Russell, who promptly seduced Vivien (for her own good, of course). Did the poet know? As Crawford observes, Eliot’s early work is replete with sexual yearning and uncertainty, his later poetry rife with sexual disgust. The marriage of “Tom and Viv” proved a disaster, but it gave the world “The Waste Land.”

The final chapters of “Young Eliot” focus on that poem’s creation. Crawford argues that Eliot learned a lot from the serialized chapters of Joyce’s “Ulysses” and that the novel’s disjunctions, its mingling of high and low styles and its mythological framework, were a far greater influence than commonly acknowledged. Not that he doesn’t admire the brilliant editing by Ezra Pound, who cut and chiseled the rough draft into its final form. Poignantly, Crawford closes his superb biography with Tom picking up the first edition of “The Waste Land” and realizing that from that moment on he was, forever more, T.S. Eliot.

Dirda reviews books for The Washington Post on Thursdays.