Allegra Coleman is Hollywood's latest It Girl. She's the subject of New York journalist Clementine James' final celebrity profile: ''I was supposed to be insightful. I was supposed to be a bit jaded too, though surprisingly impressed by this young star's talent and presence.'' Allegra mysteriously disappears while under Clem's watch, and the public's fascination soars. Meanwhile, a chorus of Hollywood flames long since extinguished -- Gloria Swanson, Natalie Wood, and Marion Davies, to name a few -- visit Clem and share their own rise-and-fall stories. Sherrill, a magazine writer with an old wad of celebrity profiles in her own back pocket, cleverly explores fame's fizzy nature. Dishy and wise, her first novel gets bumped up half a grade for the 37-page filmography appendix that hits all the movies mentioned.