From September to May, here are an eventful few months in the life of a plucky New Jersey girl, a doctor's younger daughter who is coming of age just as her beautiful older sister begins to succumb to anorexia. At 15, Billie Weinstein, unlike her accomplished 18-year-old sister Cassie, is a rebel--and a charming mess. Her schoolwork is only adequate in a family that expects straight A's, she harbors an inappropriate crush on a local gas-station attendant called Dom, and her beloved best friend Tiffany is the school hood. Billie's father, a surgeon and a dictatorial though fundamentally loving dad, has successfully coached and coaxed Cassie into her freshman year at Cornell, his alma mater, and now is turning his watchful gaze on Billie, who is cramming for PSATs. She's also tepidly dating a boy named Vinnie, captain of the wrestling team, and secretly communicating with Cassie, who's away at college and giving veiled hints of disturbing, self-destructive episodes. When Cassie comes home for Christmas weighing 95 pounds and refusing to eat, chaos erupts. Billie's father decides to ``fix'' the situation by forcing Cassie to eat (she doesn't); Billie's mother weakly intercedes; and Cassie steadily deteriorates, losing her hair, becoming too weak to walk, eventually having to be hospitalized. In a riveting, powerful scene set in the family car on the way back from a hospital visit, Billie, ordered by her father to take the wheel and practice driving, is so criticized, controlled, and belittled by him that she pulls over, flees, and hunts up Dom, who sullenly takes her virginity and then gets drunk. Interesting subplots abound, meanwhile, in a novel that keeps moving and doesn't fall back on false reprieves or sudden saving changes of character. Cassie and her parents remain locked in a battle of expectations and resistance; only Billie sees the family pattern clearly enough to begin to escape. A persuasive, well-rendered, and rich first novel about family systems.