THE LIVES of writers are supposed to be wildly indiscreet. Nights of serious drinking alternate with afternoons exhausted by ill-advised love affairs with unsuitable companions. Travel leads inexorably to dissipation, and the young man who left Harvard bright-eyed with promise ends his days smoking hashish in Tangier or reliving Malcolm Lowry's Under the Volcano.

One might think that critics, those calm Olympians of the book pages, should be different. After all their job is to judge--one expects a solid bedrock of level-headedness. But not so. Edmund Wilson put away a bottle of Scotch a day, and enjoyed priapic escapades that are the envy of lesser mortals. John Jay Chapman, a brilliant turn-of-the century social and literary reformer, burned off his hand out of jealousy and anger. And Van Wyck Brooks, whose life Raymond Nelson has succinctly and briskly set down, went absolutely bonkers for five years.

Here, in brief, is the story. Out from Harvard in 1907, young Brooks gradually works his way up to becoming a firecracker magazine critic; in 1920 he writes a controversial book, The Ordeal of Mark Twain, which maintains that the Lincoln of our literature never grew into a mature artist, largely for Freudian reasons. Soon he is the Harold Bloom of his day--read, argued about, inevitably there.

But the wheel of fortune turns. Family pressures, an unresolved love affair, uncertainties about his finances and career, writer's block, all nudge Brooks into a nervous breakdown, then madness. He is haunted--and this could happen only in literary America--by the spirits of Emerson and Henry James, who berate him for failing to do them critical justice. Poe-like, he grows to fear that he will be buried alive; eventually he pleads with his wife to take him away from the hospitals and allow him to starve to death in the woods.

And then, gradually, unexpectedly, Brooks recovers. When his mind clears in 1931, the world has changed even more than he has. No more an eminence, he finds himself a has-been, scorned by Marxist and New Critic alike. But now, largely through a special trust fund set up by his wife's mother, Brooks is able to devote himself entirely to study and scholarship. He decides to read American literature entire and compose the nation's literary history, the result being his five-volume masterpiece Makers and Finders. Beautifully, almost sweetly written, jammed with odd facts and juxtapositions, its component works--such as The World of Washington Irving and The Flowering of New England --become, unkindest cut of all, best-selling Book-of-the-Month Club selections. Serious writers and critics now utterly dismiss him as just too-too middle-brow for words. Nevertheless he persists in his long project, finishes it, and dies laden with shallow honors but without influence or followers.

As a biography Van Wyck Brooks: A Writer's Life is only so-so--Nelson doesn't quote enough Brooks for my taste, and his style is only competent-plus--but as an object lesson in the destiny that can await even the best of literary folk, it's invaluable. Any kindly uncle with a niece or nephew anticipating a career in letters might do well to hand over a copy.