The first volume of Zachary Leader’s new biography of Saul Bellow covers the first half-century of the author’s life, which he himself called “a struggle of fifty years.” Photograph by Truman Moore / The LIFE Images Collection / Getty

I’ll confess: I savored “The Life of Saul Bellow: To Fame and Fortune, 1915-1964,” the first of the two volumes of Zachary Leader’s new biography of Bellow, as if it were cake. Its text is six hundred and fifty pages long, with another hundred and fifteen pages of endnotes that can be read straight through like a cubistic condensation of the book. I’ll go farther: it may be the most purely delicious literary biography that I’ve come across. Leader’s calm, gradual, but serenely excited prose vibrates with the joy of his thought coalescing with his subject, Saul Bellow.

Leader’s research is prodigious—this volume carries only through 1964, when, at the age of forty-nine, Bellow rose both to fame and fortune thanks to “Herzog”—but the deployment of knowledge never feels gratuitous. Leader seems to have a thematic concordance to Bellow’s complete oeuvre (published and unpublished; fiction, nonfiction, and epistolary) in his head, and the correlations that he finds between the life and the work are often vertiginous.

It would be tempting to say that Leader discovers that almost all of Bellow’s fiction consists of romans et contes à clef and that, in this critical biography, the biographer discovers the keys and delivers them on a chain to the reader. But rather, the book conveys the feeling that it’s Bellow’s life that was lived à clef, that it isn’t the fiction that’s unlocked by the life but, rather, the life that is opened up by the fictions to which it gave rise. The book contains an exquisitely subtle, insightful, dramatic teasing-out of the thoughts and impulses below the surface of the writing, and of the literary impulses arising below the surface in the course of life. For all its wealth of information, Leader’s book is dynamic—it’s not a collection of well-ordered facts but the drama of a mind in constant, roiling action. In this way, the biography demands a musing, contemplative andante to join Leader on a stroll through byways that suddenly lead to open and mighty vistas, doubling back to look at dead ends, crawling through barely passable thickets to consider the allure of paths that Bellow probed and tested and then spurned.

The main subject of the book is the first half-century of Bellow’s life, which he himself called “a struggle of fifty years”—his infancy in Canada, his childhood and youth in Chicago, the poverty and stormy life among his parents (Russian-Jewish immigrants), siblings, and extended family. From his youth onward, he lived an amazingly full life—filled with sex and romance (sometimes together), a wide range of intense friendships and bitter disputes, intellectual adventures, political action (he was a Communist, then a Trotskyist), sudden changes in circumstance, and wide travels—many schools, many jobs, many cities, many countries. Through it all, the constant was writing. His literary calling arose while he was in high school; as an eighteen-year-old at the University of Chicago (where he didn’t stay long), he “was now open about his ambitions, always carrying a briefcase full of his stories and manuscripts . . .” Bellow married young and was supported by his wife and her family while he trained himself to write—but didn’t sell a story until he was twenty-five, in 1941. That story, however, was published by the Partisan Review, the leading intellectual journal of the time, which would prove to be a crucial association for Bellow.

Though Bellow published two novels in the nineteen-forties, he didn’t make a living as a writer (in fact, he wouldn’t do so until 1964, at the age of forty-nine). Throughout the thirties, forties—and, for that matter, through the early sixties, until he was nearly fifty—Bellow pieced together an income with freelance teaching jobs, freelance writing jobs, grants, fellowships, lectures, and scant advances (which nonetheless left him thousands of dollars in debt to his publisher). He married, divorced, married, divorced, and married, had alimony and child support to pay, while wrenching the time to write from his whirlwind of practical demands and emotional disturbances.

Leader gives full weight to a moment of enlightenment that’s as crucial to American literary history as the thirty-seven-year-old Jean-Jacques Rousseau’s happenstance glance at a newspaper ad en route to Vincennes was to French intellectual history: the moment when Bellow gave his voice free rein. It takes place in Paris, in 1949, when the thirty-four-year-old Bellow, sustained by a grant and an advance, was working on a novella, “The Crab and the Butterfly,” which he later described as the tale of “two men in a hospital room, one dying, the other trying to keep him from surrendering to death.” It hardly seemed a burst of youthful vigor from a writer who, though highly esteemed within the profession, was largely unknown and considered more promising than accomplished. Then, on a stroll in Paris, working glumly on this glum work, Bellow caught view of water rushing through the street from a hydrant: “I remember saying to myself, ‘Well, why not take a short break and have at least as much freedom of movement as this running water.’”

The quote is from Bellow’s interview with Philip Roth, published in The New Yorker in 2005, several weeks after Bellow’s death, which takes its title—“ ‘I Got a Scheme!’ ”— from a childhood friend in Chicago whom Bellow recalled while watching the water flow, and who became the subject of the epochal novel that resulted, “The Adventures of Augie March.”

Along with his past, Bellow liberated his voice; the novel, as Leader details, virtually poured out of Bellow, in a great rush of demotic flamboyance. It was Bellow with the superego unlatched. The street life of the young man from a Russian-Jewish family, with his full-blown new American identity, came bursting forth (“free-style,” as in the novel’s famous first paragraph). The tumultuous passions of his own travels and travails, his family and friends—and politics and sex—were exalted as an exemplary literary subject.

The secret story is why it took so long to liberate Bellow’s voice—why the multilingual immigrant family, filled with Yiddish and French and Russian, filled with hyperbole and invective, the music of the home and of the streets, didn’t find its way into Bellow’s work until then. What now appears to be the obvious thing for the young writer, easily clichéd—the twenty-three-year-old who writes his or her quasi-autobiographical bildungsroman, about family, lovers, schools, and literary ambitions and struggles—was something that Bellow didn’t consider.

He wasn’t alone. Norman Mailer, born in 1923, who published his first novel in 1948, didn’t do it. Bernard Malamud, born in 1914, a friend of Bellow’s from the early fifties (they met in Oregon, in 1952, where both were teaching, while Bellow was completing “Augie March”) didn’t do it. But Philip Roth, born in 1933—and writing after the publication of “Augie March”—did it, thanks to Bellow’s novel. In a passage cited by Leader, Roth said, “These were Jews and Jewish families and here was a guy making literature out of them, and that was a great revelation to me.” (Roth met Bellow in 1957, at the University of Chicago, where Roth was working as an instructor.)

There’s a Roth missing from the index of Leader’s book, but it’s not Leader’s fault: Henry Roth, whose first novel, “Call It Sleep,” came out in 1934, when Roth was twenty-seven. It’s a largely autobiographical book about a Jewish boy growing up in a poor immigrant community in New York; it gives a harrowing view of tenement life, and it’s told with a rich vernacular that renders Yiddish into English. It may be one of the great literary tragedies that the book remained virtually unknown at the time of its publication; it’s easy to imagine it having, on the twenty-ish Bellow, the impact that “Augie March” had on the twenty-ish Philip Roth.