Linda Simon, following the success of works on Gertrude Stein and Alice Toklas, here tackles a tough subject, Thornton Wilder. Going from a pair of literary eccentrics to a man as enigmatic as Wilder is a major jump. Simon doesn't quite suceed, but her effort is one others can build on.

Not only is Wilder himself something of a mystery - he was unassertive, wary of publicity, belonged to no coterie, never married, and seems to have practiced kindness - his lack of sustained critical acceptance also is puzzling. Wilder's writing had been in eclipse for 25 years before his death in 1975, but he had trouble sustaining critical approbation even during the heady era of the early triumphs.

And what towering triumphs they were! Wilder's first book, "The Cabala" (1926), sold poorly but caught the attention of some reviewers, among them Malcolm Cowley. The next year, however a thin volume emerged which begins, "On Friday noon, July the twenieth, 1614, the finest bridge in all Peru broke and precipitated five travellers into the gulf below." One hundred and forty-eight pages later it ends: "But soon we shall die and all memory of those five will have left the earth, and we ourselves shall be loved for a while and forgotten. But the love will have been enough; all those impulses of love return to the love that made them. Even memory is not necessary for love. There is a land of the living and the land of the dead and the bridge is love, the only survival, the only meaning."

The message and the skill with which it was crafted overcame the exotic locale and characters and "The Bridge of San Luis Rey" became a popular and critical success. It sold 300,000 copies the first year (this was before book clubs) and provided Wilder the first of three Pulitzer Prizes.

With this one book the young Wilder joined Fitzgerald and Hemingway at the top of American writing. He followed this success with "The Woman of Andros" (1930), set in pre-Christian Greece ("Human beings are fully alive only in rare moments...for our hearts are not strong enough to love every moment.") Then in 1938 came his play, "Our Town" ("Oh, earth you're too wonderful for anybody to realize you"), a work which was to become among the most popular of this century. "The Skin of Our Teeth" (1942) and "The Ides of March" (1948) rounded out his best work, though he continued writing almost to his death.

Why was Wilder accorded so little lasting critical regard? Part of the reason I alluded to above: He lived quietly without scandal; he was a nice guy and, let's face it, our culture often eats nice guys. He did his work well with rigor and grace. But critics were bothered that he also taught school and that he divided his attention between writing novels and drama.

Cowley believed Wilder missed out because, unlike Hemingway and Faulkner, he wasn't concerned with the manners of the group but with the morality of the individual: a tougher commodity to sell. Time, he believed, is panorama rather than process; everything that happened might happen anywhere and will happen again (his favorite teacher had once told him "Every great work was written this morning"). Thus he modeled much of his work on classical themes. The critics felt that this was easier than experimenting, more evidence of doing the thing at less than full throttle. He was attacked for elitism, for making his universe "a museum, not a world." Wilder responded much later and very softly, "I am not interested in the ephemeral - such subjects as the adulteries of dentists."

It is difficult to find in Simon's book any fault with Wilder. Occasionally he showed poor judgment: putting Gertrude Stein on a par with Walt Whitman (a case of friendship prevailing over thought) or easing up on his puritan integrity to the point of letting Frank Sinatra sing the Stage Manager role in a TV musical version of "Our Town" (Wilder said it kept him in martinis for a year).

A somewhat different picture appears in R. H. Goldstone's biography, which was published shortly before Wilder's death. Goldstone writes that Wilder grew crotchety as he grew older, that he was unable to sustain friendships, and that he was "neutral" sexually (a judgment shared by Gertrude Stein). Simon, on seemingly slight evidence, has him homosexual. These and other differences indicate a need for more digging by future biographers.

Simon, in her desire to publish hurriedly, has not gone into the Wilder enigma deeply enough to reconcile these discrepancies and to give us more of the entire man. What she has given us is informative, but it is too little and too soon.