By Clarissa Cruz
Updated August 20, 1999 at 04:00 AM EDT

With his affable, teddy-bear demeanor and casual attire, thriller maestro Peter Straub doesn’t look like someone who would give famous fan Stephen King the heebie-jeebies. Especially when he proudly ticks off his offspring’s collegiate choices (USC and Oberlin) or roots around a cluttered room for an ashtray, cheerfully settling on a plastic trash bin for the remains of his American Spirits. But the 56-year-old Straub — author of 14 novels, including best-sellers The Hellfire Club, The Talisman (cowritten with King), and Ghost Story — is terrifyingly accomplished in the art of horror.

And make no mistake, scaring the bejesus out of readers is an art. ”I’ve always thought you’re cheating if you don’t try to write a thriller as well as any other novelist would try and write a novel,” Straub says. ”You’re supposed to have depth of character, you’re supposed to care when a character is injured because they’re not just pawns on a chessboard. Otherwise, who cares?”

There’s no shortage of memorable players in his latest effort, Mr. X (Random House, $25.95), a classic doppelganger tale with supernatural elements, passages of H.P. Lovecraft parody, and an unexpected stable of wickedly droll oddball characters mixed in. The story revolves around an attractive New York City professional who returns to his hometown when his mother falls ill. He then unearths a heap of way-past-dysfunctional family secrets, among them time travel, levitation, slave trading, and witchcraft.

”I felt free to indulge in the supernatural…into a territory where more or less anything goes,” Straub explains, admitting that Mr. X is a more fantastic departure from his past thrillers. ”I think the curves [in this story] are rounder, and the accelerator works more smoothly.”

Which doesn’t really leave your hands free to cover up your eyes during the scary parts.