To Isaac Bashevis Singer, ironic self-deprecation is a way of life.

Told nearly a decade ago that his books were attracting wide numbers of American readers, he gave an elegant shrug and said in his lilting, accented English, "not like Norman Mailer."

Told the same thing two years ago, he shrugged again and said, "I don't think that I am famous now, but if you say so, who am I to say no?" He added mischievously, "Today, to be famous you have to be Frank Sinatra."

Now that he has won the Nobel Prize for literature, however, even Sinatra may have to step aside.

In person Singer is a bird-like man with sparse, wispy white hair and nervous hands that fold and refold almost of themselves as he talks.

The dark suit he habitually wears enhances the gravity of his 74 years, and in many ways he is typical of the elderly Jewish residents of New York, fearful of walking the streets of his Upper West Side neighborhood at night and spending half the year in Miami Beach.

Yet for all this, and for all the tentative, almost timid graciousness with which he greets visitors, there is something in his manner - a bite, a sharpness - that sets Singer apart, that says that he is hardly as innocent as he looks.

Look closely at the arresting, demanding eyes and the sharp lines in his face and he doesn't look innocent anymore but impish, an aging Puck. He is not always what he seems.

Associated closely with the small communities of Eastern Europe, Singer has in fact lived in New York for more years than in his native Poland. And although he still does all his writing in Yiddish, generally on a piece of hard cardboard that "I put on my knee and scribble on," Singer's sexual frankness and deviance from the language of sentimental tradition have put him well outside the mainstream of Yiddish literature.

"I like to write about sex and love, which is not kosher to the Orthodox people," he explains. "I believe in God, but I don't believe God wants man to run away completely from pleasure. If he has created men and women with a great desire to love and be loved, there must be something in it; it can't be all bad. Love and sex are the things that give life some value, some zest. Miserable as flesh and blood is, it is still the best you can get."

In 50 years of writing, Singer has produced an enormous body of work - a body whose exact dimensions are unknown to his American audience since healthy chunks of it remain untranslated. He has done everything from memoirs to journalism to children's books, but his world emerges most clearly in novels like "The Slave," "Satan in Goray," and "The Magician of Lublin" as well as in short-story collectioon like "Gimpel the Fool."

It was Saul Bellow's translation of that title story in a 1953 Partisan Review that first brought Singer an English-speaking audience.

Singer's works, set in an era of European Jewry that ended in the concentration camps, are paradoxical: at once concrete and fantastic, supernatural and down-to-earth. "I demand from a story to be both mystical and real at the same time," he says. "Even if I write miracles, these miracles are embedded in reality."

He writes with equal defteness and plausibility of demons and dybbuks, of surly peasants and agonized rabbis of lust and impotence, of death starvation and ecstasy. "In my stories," he has written, "it is just one step from the study house of sexuality and back again." Critic Irving Buchen calls him "a conservative sensationalist" and writes that "his fictional world is so jammed with the dead that there does not appear to be any room for the living."

Yet the living in his books are so illuminated by the simple crystal purity of Singer's style that he can create character with a single sentence, as in: "He was a short, broad-shouldered man; he looked as if he had been sawed in half and glued together again." He is a writer at ease with wonder, a writer who feels "literature without passion is like bread without flour."

The paradox continues on a personal level, for Singer describes himself as both "a skeptic and a mystic." Though a constant, inveterate questioner, he feels "the very fact that I exist is a mystery to me. I may not believe what is written in holy books, but I feel the mysteries of creation are right near me. I walk on mysteries."

As he is set apart from the Yiddish novels, so is he set apart from most of modern fiction. "I don't see great writers in this century," he says, seemingly weary with the effort of looking. "The modern writer is so eager to be profound, to be symbolic, to show off his greatness, that the reader cannot enjoy him anymore.

"Never before in the history of literature have the readers been so fooled, so hypnotized against their will, to call mediocrity greatness. The net result is that we have so many so-called celebrities, but there is nothing to celebrate."

So when Singer wants to read a good book, he goes back to the likes of Tolstoy and Dostoevsky, the people he calls the "masters" and the people in whose footsteps he is still anxious to follow.

"The masters were all great storytellers, and they wrote in a very clear way, they tried their best to be clear," he explains. "Look at the Bible. The Bible is not obscure, it is wonderfully clear, yet I am sure that when Moses came down from Mt. Sinai, the intellectuals of his time said, 'For this he had to go up to heaven? Couldn't he have brought us something more profound?' But heaven is not interested in phony statements." And neither, obviously, is Singer.

Convinced that whatever popularity he will admit to results from his firm adherence to the tradition of storytelling - "I don't hide behind puzzles, riddles, symbols which mean nothing" - Singer has turned a great deal to writing books for children.

"Children are my best readers; I only wish adults should behave in the same way," he says slyly. "A child loves a story, you cannot give to a child a book without a story. He is an independent reader, he is not influence by reviews, because children do not read reviews. He is not influenced by authorities, you can tell a child Gold Almighty himself wrote a book, and if the child does not like it he will reject it. Where do you get among adults such readers nowadays?"

In addition to all his other singularities, Singer is also half of one of the few novelist brother teams in literary history. His elder brother, I.J. Singer, was the author of "The Brothers Ashkenazi," "Yoshe Kalb" and other novels and was in the younger brother's words Singer's "master and teacher."

The elder brother introduced Singer to secular literature, giving him a Yiddish translation of "Crime and Punishment" when he was 10. He was also the first to break with the family's Orthodox religious tradition - the boy's father was a rabbi in a poor section of Warsaw. Singer started out as a proofreader - "the kitchen of literature," he calls it - and wrote his first stories in 1926. His first novel, "Satan in Goray," was published in 1935, the same year Singer followed his older brother to New York.

His first years in the new land, however, were distinctly unpromising, almost catastrophic. "Since I didn't know English, I felt very bad," he says. "I had a feeling Yiddish is going to last here only a few years, I was afraid I'd be a writer who has written only one book."

He felt, he has said, like he was in a cemetery; seven years went by before he was able to write again. Now, however, Singer says he will never forsake his original tongue: "If I would be the last man to speak Yiddish, I would still write in this language. I know this language best."

A latecomer to fame, Singer feels that's the way it should be. "I had many years of complete privacy and they didn't do me any damage," he says wryly. "I never became bitter. I understood that when a young man begins to write, the whole world is not going to embrace him immediately as they do in this country. Here, when a young man writes two stories which make sense they celebrate him already as a genius. A young man sometimes loses his head, he really thinks he's God's gift to humanity."

All this strikes Isaac Bashevis Singer as a bit droll, a game he is unable to play. "A writer who is famous in later years takes it with a grain of salt. A person who is famous at 26, he's forgotten at 36. One is not famous forever."