"I have nightmares," says Peter Straub, who makes his living from nightmares. "I am walking through endless corridors in an enormous hotel, and I know I have a room but I don't know where it is, and I have no key."

Straub is in the lobby of the Hyatt Regency, where he has arrived a bit early and his room is not yet ready. He knows he has a room, but he doesn't know where it is, and he has no key.

But he has nothing to fear: At 38, Straub is one of America's most successful writers in the horror-suspense genre. His novel "Ghost Story" (1979) has sold about 2 million copies in paperback alone; another, "Shadowland," has just been published. Next year he will collaborate on a novel with terror impresario Stephen King. And now there's the movie, "The Haunting of Julia," in which he has a sentimental but not a financial interest.

"I've made all the money I'm going to make from that picture," says Straub. "In fact, I gave some money back so they could finish making it."

"The Haunting of Julia" was shot in 1976 from Straub's second published novel, "Julia," a dead-child-and-haunted-house chiller, and is being brought back to the box offices after dying painfully on its first run.

"The first time I saw the film, I came out very disturbed," Straub recalls, "and I didn't know whether it was because of what they had done to my book or what the picture did to me. Now, I an still disturbed by the movie, but I am no longer disturbed about what they did to my book." That's a good attitude, since "Ghost Story" is now being filmed with a cast that includes Fred Astaire, Melvyn Douglas, Douglas Fairbanks Jr., John Houseman and Patricia Neal.

Straub never intended to write horror stories. His first novel, "Marriages," had been published in England and America in 1973 and almost immediately dissappeared without a trace. He was working on a revision of his second novel, "Under Venus" (still unpublished) when the change occurred. "I wrote 'Julia' because I was desperate," Straub says. "I was dead broke and in danger of going under. I wanted to stay alive and stay married and you need money for that. So I went to my agent and asked her, 'What will I do?' and she told me, 'Drop that book you've been rewriting forever and write a Gothic.'

"I wasn't sure what she meant then and I'm still not sure -- something like Mary Stewart, I suppose. But I wanted a story that would appeal to a publisher. At that time I was living in England, near Hampstead Health, so I would go out each day walking on the health and jotting down notes.I did that for a month. Then my notes began to scare me, and I knew I had something."

His background until then had been academic and "Under Venus" reflected it. "It is about an American composer returning to a former home town in the Midwest to meet a former mistress and conduct a concert of his music at a college where he had once taught," Straub says. "It is very intense -- full of the feeling of a supernatural novel, although there is nothing supernatuaal in it. At that time, I was very influenced by Iris Murdoch."

He had wanted to be a writer since he was a child in Milwaukee. "All I knew," he says, "is that I was extremely verbal. I hungered to read when I was 2, and taught myself to read when I was about 5. As a kid, I read everything under the sun, from adult books to the backs of breakfast-cereal boxes. In grade school, I wrote with an adult style and that got me into trouble: They thought my father was writing my homework.I thought about writing a lot, but didn't have anything to write. It seemed impossible, so I turned to English studies in college -- first a Bachelor's degree at the University of Wisconsin and then a Master's at Columbia. It seemed a safe and respectable way to be close to the world of writing."

After teaching English at a boys' school in Milwaukee for two years, "I didn't want to continue," says Straub. "My wife Susan and I took our savings and moved to Ireland for a few years. The plan was to get a Ph.D. and come back to get a better job. Then, in Ireland, I suddenly realized what the trouble really was: I had always thought of myself as a novelist although I had not written a novel. I could feel fiction growing inside me, characters and situations forming themselves in my mind as I walked down the street. This was my second summer in Ireland, and I knew that it was my last chance, so I sat down and wrote 'Marriages.' This was the most joyful time of my life, and it felt even better when 'Marriages' was accepted by the first English publisher I sent it to and then sold to Coward-McCann in America."

The Straubs decided to move to England, and shortly thereafter came the fateful writing of "Julia," a long, tangled tale of guilt, insanity and eeire, unexplained deaths. It opens with a young girl strangling to death at the breakfast table while her parents helplessly watch it happen. The Straubs, who now have two small children, had none at the time. "I can't kill kids like that any more, now that I have two of my own," Straub says. "But adults are still fair game."

Perhaps because she was so impressed by "Julia," Susan Straub keeps tacked to her kitchen wall in Westport, Conn., a set of instructions for the Heimlich Maneuver -- a technique for saving people who are choking on food, which would have stopped the plot of "Julia" right at the beginning.

Although he now has four novels of horror and the occult published and a fifth, "Floating Dragon," partly written, Straub has no formula for fright. "This isn't something you think about while you're doing it," he says. "That would spoil it. It's something you do afterwards, and if you get serious about it you begin to sound like you spent too much time in graduate school."

But he will hazard some ideas. "Guilt feelings are probably the reason why we seek out that experience -- and particularly why we seek it out in books and movies. In real life, terror is unnerving, dehumanizing, but it may be therapeutic when you turn it into fiction."

Monsters, he believes, are "projections of our own most violent and destructive traits. Now that I have kids, I am beginning to understand why children love them, why they will stomp around on stiff legs making strange faces and saying, 'I am Dwacula.' It's a license to have those urges, a recognition that they exist and a harmless way to express them. As adults, we respond to these feelings even while we experience guilt about having them."

Straub is fairly sure that his novels represent his own secret fears in some way, but he does not care to examine them. "Personally," he says, "I practice all kinds of superstitions. I don't walk under ladders, and I don't light three cigarettes on one match." He pauses a moment to light one cigarette with a lighter. "It's not that I believe in these things, but why flaunt it -- why take chances?"

Old houses are among the things that Straub finds spooky, although he does not include the 80-year-old Victorian house he owns in Westport, Conn. "It was unoccupied for a long time and the rumor in the neighborhood was that it was haunted." It may be the starting point for Straub's next novel, "The Talisman," which he plans to write next year in collaboration with friend and colleague Stephen King. "Steve is working now on a Bible-length book and I'm working on an average-size book," he says, "so we'll probably finish at about the same time. We plan to sell "The Talisman' this fall and then write it together next year. The original idea was that it would start at my house in Connecticut and finish at his house in Maine. That would give us a lot of seacoast to cover."

The friendship with King began through mutual admiration. "Back when he was unknown," Straub recalls, "my publisher sent him galleys of my first two books and he sent back glowing statements on them -- not the usual blurb, but long, thoughtful statements. Then I was in a bookstore one day and I saw his name on a book and I thought I should buy it out of loyalty -- so I bought a hardcover copy of 'Salem's Lot' and it knocked me over. He was trying to do the same thing I tried to do -- investing the genre novel with all the seriousness we had as novelists. I thought, 'I have found a brother,' but I didn't write to him until after I had read 'The Shining.' He's probably the only writer I could unselfconsciously be good friends with. I hope our collaboration does not destroy this." Selling the book should be no problem -- Straub says that his publisher shouted "I'll buy it" as soon as he heard of the project.