Marvin's not sure whether he's turning into a girl, whether he's just imagining what it's like to be a girl, or whether he's having a nightmare. Is he weird to want to play hopscotch and to wish he could wear sparkles on his clothes? As in the other easy chapter books about Marvin, Sachar writes for beginning readers with a comic simplicity that is never banal. Here he gets a lot of fun out of the identity confusion, and kids will love the frankness about grade-school gender wars and social taboos. There are no neat answers, but a lot of droll questions, including What's normal? The cover, with Marvin staring at a girl's reflection in the bathroom mirror, will draw kids right into the farce of the story. (Reviewed Nov. 15, 1993)