A.A. MILNE The Man Behind Winnie-the-Pooh By Ann Thwaite Random House. 554 pp. $29.95

THE SUBJECT of this biography would have groaned at its title. Pooh may have guaranteed his creator a more than comfortable income for life, but he also became a terrible literary incubus. The assistant editor of Punch, the master of light verse and even lighter essays, popular playwright (Mr. Pim Passes By, The Dover Road) and novelist (Two People, Chloe Marr), A.A. Milne saw himself as that now almost extinct species, a man of letters. So he was, and in his day a very successful one, which at once places him not only in his age, but also of it. No formula for success dates faster. By the mid-'20s this Edwardian gentleman-liberal (radical, he thought) was looking distinctly passe'. Pooh and Co. changed all that.

It was not, for Milne, a welcome way to be rescued. Conan Doyle yearned to be appreciated for his historical novels; the public wanted Holmes, and the public was arguably right. In old age Milne, still versifying with all his old verve and blissful lack of self-knowledge, had this to say:

If a writer, why not write

On whatever comes in sight?

So -- the Children's Books: a short

Intermezzo of a sort;

When I wrote them, little thinking

All my years of pen-and-inking

Would be almost lost among

These four trifles for the young.

Anyone who today, like Ann Thwaite, takes the trouble to hunt out the rest of Milne's forgotten oeuvre will have to admit that it's pretty awful stuff: much ado about very little, slackly verbose and written with an arch facetiousness that grates on the nerves. In his autobiography Milne declared: "I know no work manual or mental to equal the appalling heartbreaking anguish of fetching an idea from nowhere." "Nowhere" is the key word. One wishes he'd spared himself the trouble.

Even the best of the plays (e.g. The Truth About Blayds) are bulked out with mushy dialogue that does little to advance the action, and suffer from vestigial or heavily contrived plots. (I vividly remember, years ago, being offered the title part of Oliver Blayds, only to discover that Blayds was 90 years old and killed off at the end of Act One, a fact for which I felt no more disposed to forgive Milne than did the first-night critics.) Milne as man of letters was a middlebrow darling of the dress circle and the lending libraries, whose works, by and large, had the mayfly evanescence of a Victorian three-decker novel. It was indeed the four children's books -- When We Were Very Young (1924), Winnie-the-Pooh (1926), Now We Are Six (1927) and The House at Pooh Corner (1928) -- that kept his name alive. The main problem for any biographer of Milne, indeed for any student of children's literature or the psychology of writers, is to figure out why.

Ann Thwaite tries to establish Milne's profile by a slow, careful, skilfully deployed accumulation of detail, based on free access to family papers and interviews with surviving friends and relatives. I doubt whether we will ever learn more facts about Milne than are gathered in this biography: a happy childhood and schooldays, the apprenticeship under Owen Seaman at Punch, marriage to bossy Dorothy ("Daff") de Selincourt, a brief traumatic spell in the trenches during World War I, the postwar literary success in the pre-war mode, the apotheosis through Pooh and Christopher Robin, the decline of popularity, rural lfe in Sussex (the setting of the Pooh stories), the endless letters to the London Times.

Thwaite is best on aspects peripheral to the main issue -- Milne's strong affection for his elder brother Ken, his rather wobbly liberalism (a professed pacifist, he nevertheless fought in the First World War and damned P.G. Wodehouse publicly in the second for the latter's harmless if misguided radio broadcasts from Germany, where he was briefly interned), his essential decency and humanity, his literary and theatrical friendships. Yet one is left at the end with a whole bunch of unanswered questions, sexual, social, psychological. Alison Lurie included the Pooh books in a gallery of subversive children's literature ("If Pooh is the child as hero," she wrote, "Christopher Robin is the child as God") and was right to do so. There is a real radicalism, and universalism, about Milne's assumptions in these four children's books, where he assumed a persona that let him drop all his social and literary conventions. (Has maternal bossiness ever been skewered more accurately than is the portrait of Kanga?)

Another point that needs making, though Thwaite doesn't make it, is the extraordinary change in prose style that takes place in the two Pooh books, which can be only partly explained as Milne consciously doffing his grown-up literary hat. Gone, along with conventions of which they formed a symptom, are the insubstantial prolixity and upper-middle-class cutesiness, the social conservatism and cliche-ridden Punch banter. Instead we have sharp, sardonic, clipped sentences, touched with light irony, where every word packs a well-directed punch, while the tone achieves the timeless resonance of a true classic. How did this happen?

Strong conventions breed their own subliminal creative escape-routes, as the Alice books testify. Milne's nervous social and domestic tics seem to have followed a similar route. In two of the children's books he took advantage of his technical skill in that quintessentially English medium, formal light verse: ideal both for getting round serious problems by trivializing them and for being exquisitely bitchy in a manner that disarms complaint. Decoding the social messages in the poems can be revealing.

Thwaite tries to show that, despite his son's, and indeed his own, testimony to his distaste for children's company, Milne in fact spent much more time with Christopher Robin (or Billy Moon, as the family knew him) than has hitherto been admitted. If he did, it was (the evidence, again, is plentiful) to relive his own childhood vicariously and pick up useful literary copy: Writers seldom admit their own ruthlessness, least of all to themselves. This biography of a literary conundrum spends -- perhaps understandably -- little time on his writing as such. Instead we get a tantalizing social portrait of a decent, unadventurous, successful bookman, a humorist who gave his public what it wanted, including a well-laundered pile of ide'es re'cues, and never quite understood why the passage of time and changing mores left him on the beach, a stranded literary whale. In his memoirs, as an example of how not to write a play, Milne gives us a couple of rivetingly disjunctive pages of "realism" that read like early Pinter. Fashion, alas, won again. How lucky for all of us that he never quite realized what he was up to in the children's books. Peter Green, Dougherty Centennial Professor of Classics at the University of Texas at Austin, is the author of "Kenneth Grahame: A Biography," among many other books.