Liar, Liar

""Everything had been easy until sixth grade,"" laments DeClements's (Nothing's Fair in the Fifth Grade) refreshingly candid heroine at the opening of this thoughtful if inconsistent novel. The source of Gretchen's difficulty is Marybelle, a new girl in school whose first misstep comes during a ""demonstration talk,"" when she shaves off part of wealthy, pretty Susan's thick strawberry blond hair and insists it was a mistake. The lonely and troubled Marybelle continues to weave a hopelessly tangled web until--in a final fateful deceit--she tells the other kids at school that her mother caught Gretchen stealing something from their house. Understandably miserable when her friends then turn against her, Gretchen relies for support on her sympathetic, very credible family. The tale's climax is an eerie, intervention-like encounter, masterminded by Gretchen's half-brother, in which her classmates confront a humiliated Marybelle. Though DeClements's central characters are strong, some of the adults are two-dimensional (e.g., Gretchen's mom is pretty, flighty and obsessed with getting married; Susan's mother is exacting and elitist), and her plotting is occasionally strained (why would Gretchen's friends believe Marybelle over her?). Despite these shortcomings, the author delivers a hard-hitting message about truth-telling. Ages 8-12. (Mar.)