Sex still fascinates 72-year-old Edmund White, whose prose is always most alive when it sneaks underneath the sheets. In Jack Holmes & His Friend, White is in top form describing the erotic exploits of his two main characters Jack, a handsome gay-man-about-town, and Will, the straight object of Jack's unrequited affection as they bed-hop in New York City from the 1960s to the 1980s. The book's most virtuosic moments are also its filthiest, as when White describes Will's nether regions as looking ''like one of those mad medieval Japanese heroines in the movies with their pale faces drowned in hair pushed forward.'' But the story's fully clothed passages are told with bored indifference, as though White is as eager as his characters to get to their next sexual romp. B

