BACK IN THE 1960s, the 15th-century Dutch painter, Hieronymous Bosch, was rediscovered by seekers after psychedelics; his canvases, with their bizarre and tantalizing iconography, seemed perfect for the "oh wow" era, and so reproductions proliferated. But, for fantasy writer Peter S. Beagle, whose own works, the novels The Last Unicorn and A Fine and Private Place, were gaining a cult audience of their own during that period, Bosch was a long-held private obsession. Now 43, Beagle found Bosch for himself when he was a teen-ager and says, "At first I thought he was a modern science fiction illustrator."

So when a small publisher in California, where Beagle lives, Don Ackland of Rosebud Books, approached him about writing an appreciation of Bosch a few years ago, it didn't take much to get Beagle to agree to embark on this labor of love. "It was guesswork on Don's part. He stumbled on to a weak spot of mine." However, the project wound up with Viking, Beagle's longtime publisher, distributing The Garden of Earthly Delights as a Studio trade paperback title in conjunction with Rosebud and its new owner, Knapp Press. A sensuous mixture of art and text, the finished book pleases Beagle, who professes himself "delighted at the way they wound the pictures around my words."

"Bosch's real popularity," Beagle says of his subject, about whose life almost nothing is known and whose art will always be enigmatic, "was in his own time and now in ours. A few major studies appeared during in the 1930s; before that there was almost nothing." Analyzing it, Beagle thinks that there are distinct similarities in mood between Bosch's time and our own. "It's the sense that the world is about to end or that things are coming unravelled, or that things that have mattered aren't going to any more." Besides the overpowering fantasy element in Bosch, which appealed to the young Beagle, there's also a "writer's sensibility" which he now notes -- the use of visual slang, jokes and puns, as the artist portrays "humans overmastered by their desires."

Nephew of the painters Raphael, Moses and Isaac Soyer, Beagle grew up in a family where art was part of everyday life, and in doing The Garden of Earthly Delights, he wanted to create a book for those "people who don't ordinarily read art books. My uncle Raphael, who's now 83, would have eaten me alive if I'd written anything academic." The verdict? "He likes it." Another question: Bosch's "horrid, seething loveliness," as Beagle terms it, is certainly the stuff of nightmares. Did he experience any while he was involved with the project? "I was too fascinated to be frightened. And I've known this stuff for so long that it seems like part of my own imagination."