THERE IS A DEEPLY ingrained prejudice - deeper in America than in England perhaps - against regarding mysteries as literature, as though, ipso facto, a mystery cannot rise above a pedestrian level. A mystery, so the argument goes, can be entertaining, even engrossing, but it can never be mentioned in the same breathe with serious works.

To that, the legions of Nero Wolfe fans around the world who read his exploits in 26 languages besides English say "Pfui."

Rex Stout, Wolfe's creator, set out to be a serious writer. He wrote five novels (or nine, if four earlier works that appeared in serial form are counted) before writing his first Wolfe mystery, Fer-de-Lance , at teh age of 47. "I could have been like Steinbeck or H.G. Wells," he said at age 87. "Just another one of the good ones. But when you're making serious comment on people and their behavior, you have to put part of your soul in the work. I thought, if you're merely good and not great, what's the use of putting all that agony into it?"

So he substituted pleasure for pain and produced 42 novels and 39 novellas in the Nero Wolfe series with combined sales of more than 100 million copies.

We are all the richer for his choice. In taking up mysteries and in giving life to Wolfe, Archie Goodwin, Fritz Benner and the other characters that appear in the series, Stout created a literary world at least as palpabie as that of Sherlock Holmes. The comparison is appropriate, since Wolfe holds a place in American mystery literature comparable to the resident of 221-B Baker Street.

But Stout was not merely Wolfe's creator, he was a man of many parts - banker, writer, father, husband, champion of political causes and a horticulturalist of considerable skill. Stout's biographer, John McAleer, has more than done justice to recording the several stages of Stout's life.

McAleer's thesis is that Stout used Wolfe and Goodwin to work out his own identity. Whether or not McAleer proves the point, it's harmless enough and does not get in the way of the narrative. He portrays a life every bit as engrossing as a Nero Wolfe mystery. The full flavor of Stout's wit and urbanity comes through, as well as his straightforward, quintessentially American perspective on life and the world he lived in.

Stout's books managed to acknowledge the world they were written in without letting contemporary events dominate the story or characters. Wolfe and Goodwin are ageless: the routine of the brownstone remains ever the same, but the changing character of the world outside is acknowledged over the years.

Wolfe and Goodwin, as McAleer makes clear, embodied values that Stout esteemed - wit, grace, rationality, a Jeffersonian sense of equality and a reverence for the English language as a medium for communicating clearly and perpetuating civilization.

McAleer has not entirely left out the warts, either. Stout was sustained throughout his life by his self-assurance, but the dark side of that trait was an inflexibility that made it hard for him to admit error and an intolerance for opposing points of view when locked in political debate.

Stout died two years ago, just short of his 89th birthday and a week before his last book, A Family Affair , was published. McAleer's admirable biography is a fitting tribute to the man in whose works millions of readers have found comfort, dignity and a good-humored affirmation of life.