Ira Levin, among his other accomplishments, is the man who put the Devil on the best-seller list.

But he wants it understood that his feelings for witchcraft, possession, exorcism, reincarnation and the like are "the same feelings as anyone's.

"It's not something that I gave much serious attention to," says this soft-spoken, painstaking 48-year-old novelist and playwright. "I really don't believe in the occult. I have no quarrel with the people who do if it fills their needs."

So why do witches, seers and zombies keep showing up in Levin's work? Pure coincidence, says the author, offering a separate humdrum explanation for how each of his sinister plots came to him.

He traces the inspiration for "Rosemary's Baby," for instance, to a lecture on the importance of cycles that somehow put the notion of unnatural birth into his head.

"It struck me that the opposite side of the traditional myth of the Son of God had never been written," he explains.

After Levin repaired that omission in 1967, the floodgates of occulture swept open and out came "The Exorcist," "The Omen," "Carrie," "Ghost Story," the assorted "Draculas" and a small tidal wave of other tales of evil and the supernatural.

In person, despite a potentially sinister beard, Levin cuts a hopelessly mild-mannered figure for a man of such evil works. He is a stay-at-home type, too, and the home he stays at home in, like the man himself, is distinctly unterrifying.

"I live, I guess, as simple a life as one live in a Park Avenue apartment," says Levin from his small, tightly shuttered office, minimally decorated with memorabilia.

He is about to get married, for the second time, to yoga teacher Phyllis Finkel. But Levin appears no more sold on Yoga than on witchcraft. "She hasn't given me any lessons," he says. "She feels it might jeopardize our relationship."

Levin's main contribution to restoring the Devil's literary reputation has been as an inspiration to others. But his own works, down to and including "Deathtrap," the hit Broadway whodunit that opens at the Eisenhower Theater Tuesday, show a continuing preoccupation with dark matters.

In "The Stepford Wives" a suburban townful of housewives mysteriously turn into obedient, husband-worshipping zombies. In "The Boys From Brazil," an exiled Nazi living in Paraguay schemes to breed a cadre of Hitler clones, figuring that one of them, at least, will take the genetic hint and get a Fourth Reich cooking.

"The Stepford Wives" was inspired by a section of Alvin Toffler's "Future Shock" dealing with domestic robots.In addition, says Levin, "I wrote that just after I got divorced. I was feeling pretty bitter about the relationshih between the sexes."

"It's a book that requires a lot of suspension of disbelief," he adds.

"The Boys From Brazil" arose from a newspaper article on cloning, with multiple illustrations - to show the range of possibilities - of Hitler and Mozart. Needless to say, Levin never gave much thought to a novel about the cloning of Mozart.

As a playwright, he has shown a lighter touch. His first two plays were the adaptation of Mac Hyman's "No Time for Sergeants" and "Critic's Choice," both comedies. "Deathtrap," although a thriller, veers sharply back and forth between comedy and suspense. The author seems to be running an experiment to see just how far he can go down one road and still make a successful return trip.

"I'm very pleased about it," says Levin. "That both work: the screams and the laughs. And in a way I think they feed off each other. After you have a scare you really want to laugh. The laughs do sort of disarm you."

"Deathtrap's" protagonist, Sidney Bruhl, played by John Wood in the Broadway original and by Brian Bedford here, is a has-been author of stage whodunits trying to repeat his one early hit. When a surefire mystery play arrives in the mail from an advice-seeking newcomer, Bruhl invites him for a visit and starts hatching a murder.

The play's premise has nothing to do with the occult. But the Bruhls happen to have a meddlesome neighbor who happens to be a psychic, and Levin assigns her a pivotal role in the mystery's outcome.

All of Levin's stories tend, on cold analysis, to be staggeringly farfetched. This is part of his charm as a writer - a willingness to take a preposterous premise and execute it with care and conviction.

At the moment, however, Levin is threatening to write something less fantastic. "I hope my next book will have a very believable premise," he says.

Since he has not quite decided what his next book will be, Levin-watchers may take a skeptical view of his conversion. But even if he should devote the rest of his career to a series of children's stories about a girl and her pet chipmunk, Levin's place in the modern movement toward devilry seems assured.

He makes it a point, he says, to check up on books, movies and plays said to be in the "Rosemary's Baby" tradition. And while he doesn't appear to feel especially strongly on the subject, he takes the view that the trend has gotten slightly out of hand.

"They do get steadily more graphic," he says, citing the scene in "The Omen" in which a sheet of glass comes flying through the air and slices off David Warner's head (which then bounces vividly to the ground).

"I think that's a dead end," says Levin, "although they never seem to reach it.

"Thay's why the idea of 'Rosemary's Baby' appealed to me. Because the evil is really out of sight. These stories are always scariest when the thing is approaching through the fog."

It crossed his mind while writing "Rosemary's Baby" that the might be venturing into treacherous territory. "I had some qualms," says Levin. "I certainly didn't imagine that it would be filmed. I thought producers would not dare touch this kind of subject matter. But I felt I'll just have to go on with it. At that point I was already in the grip."

The idea of "Rosemary's Baby" and its successors may be breeding a newly superstitious generation of Americans doesn't worry Levin in the least. "I would think that seeing this sort of material presented in commercial movies and books would take the sting out of it, rob it of any real threat," he says.

In any case, Levin doesn't regard the current obsession with satanic and supernatural subjects as anything literarily extraordinary. "These kinds of stories have always been popular. I guess the films especially lend themselves to it." And he pins some of the blame - or credit - on the fact that "we're living in times when it's very hard to identify who the good guys are and who the bad guys are." The highlighting of good and evil in works of art, he suggests, may answer a craving left by real-life ambiguities. It's not an original thought, but perhaps a true one.

Levin has had some bad experiences in the theater, including the thriller "Veronica's Room," the musical "Drat! The Cat!" and his most recent comedy, "Break a Leg," which closed the same week it opened. On Broadway, he says, nothing is guaranteed. Even a show with a roster of proven box-office names can fail, and fail miserably.

But his books have all succeeded, and will go on succeeding, Levin calculates. Random House, his publisher, will print a minimum of 100,000 copies of anything he writes; and when that many copies are printed, a book gets promoted.

"Unless it's really God-awful," says Levin, "it's almost sure to make the best-seller list."

Still, he expects to continue writing plays. Even if they don't all fare as well as "Deathtrap," which now has four productions going simultaneously and whose movie rights sold for a reported $1.5 million, Levin says that "money just isn't the No. 1 consideration. Fortunately, I don't have to worry about that right now."

He is such a slow writer, he says, that at first he failed to pursue the idea for "The Boys From Brazil" for fear that somebody faster would beat him to the punch. He spends a lot of time, including just now, simply fishing around for a plot.

"I'd like to move on to richer works," he adds, "but the primary purpose will always be to entertain." Messages, as some dramaturgical scamp undoubtedly once said, should be left to Western Union.

"I really in general tend to resent works of art that make a moral point," says Levin. "In a way, when you write something sheerly to entertain, that's making a moral point, too."

The train of thought suddenly propels him onto the subject of Samuel Beckett. "If he really believed that life was as bleak as he says it is, he wouldn't be writing plays. He'd be sitting somewhere buried in sand up to his neck."

This attitude may explain why some current thrillers toy with our moral cravings only to leave us morally bewildered. But "Deathtrap" is too funny and too frightening to leave its audience any time for bewilderment.

If you think a play, by definition, can't be as frightening as a movie, don't tell Ira Levin. He saw the movie "Alien" recently, and when the audience screamed, he was delighted to note that "it was the same scream as in 'Deathtrap.'" CAPTION: Illustrations 1 and 2, no caption; Picture 1, no caption, By S. Karin Epstein for The Washington Post; Picture 2, Brian Bedford, Betty Miller and Kathleen Freeman in a scene from "Deathtrap."