The diet revolution, formally reserved for adolescents and adults, takes front and center stage in a picture book that purports to be a lesson in self-esteem. When faced with an acting audition in a local play, would-be actress Hillary the cat, formerly happy with herself, looks in the mirror and finds she is too round. Goaded on by her sister, slim Felice the diet queen, Hillary suddenly adopts the strict regimen of eating dry toast, watery soup, and a bowl of lettuce while working out at all hours on the stairstepper. The motives overtake story in a well-meaning but heavy-handed message when Hillary sees the much-admired actress/singer Nina Clophoofer, who is not only round, but happy and comfortable with herself. These cartoon creatures from Caple resemble a pleasant cross between Aliki’s characters and Nancy Carlson’s, but the story is too self-conscious and unintentionally inspiring: Children who have no weight problem and who have never considered the possibility of being either too large or too small may suddenly be checking their mirrors. (Picture book. 4-7)