Ayelet Waldman, . . Berkley Prime Crime, $22.95 (240pp) ISBN 978-0-425-18473-8

The challenges of motherhood don't hold a candle to the challenge of sleuthing for Juliet Applebaum, the heroine of Waldman's third sparkling "mommy-track" mystery (Nursery Crimes; The Big Nap). Once an L.A. assistant district attorney, now a "somewhat unwilling stay-at-home mom," Juliet uses her legal skills to look into the death of Bobby Katz, her personal trainer. The police write it off as a suicide, but no one close to Bobby, including his fiancée, Betsy, a recovering (barely) drug addict, and his uptight parents, believes that theory. Juliet juggles investigating the case with parenting her two small children, the still-breast-feeding Isaac and his older sister, Ruby. The swift and engaging plot revolves around questions of heredity and genetics. Juliet's palpable, refreshingly honest dislike for the mundane realities of parenting should resonate with many. Juliet is more mom than detective, but there's a sense she wishes it were the other way around. If much of the author's spin on the "joys" of motherhood is familiar, in one interesting thread Juliet tries to fathom her son's desire for a toy gun. Later there's a neat contradiction when Juliet goes to a range and discovers she likes shooting. This witty and well-constructed novel probably won't satisfy serious crime fans who expect passion and intensity (though some minor characters display plenty), but those with a taste for lighter mystery fare are sure to relish the adventures of this contemporary, married, mother-of-two Nancy Drew. Agent, Mary Evans. (June 4)