Eight-year-old Mandy never shows her feelings, whether she gets surprised at her own birthday party, scores the winning goal in a soccer game, or is stung by a bee. Instead, she draws her feelings as monsters in her sketchbook. When her older sister leaves home to go to college, Mandy spends all day drawing such monsters. That night they all escape from the book and run away, except Happster, who explains that Mandy must tell each monster how she feels about it in order for it to return to her sketchbook. As Mandy and Happster find the other monsters, she starts to experience the feelings she has hidden in each. Navarrete draws Mandy's monsters as bright, colorful, childish crayon drawings. Without becoming didactic, Williamson's story lets young readers know that it's okay to feel happy, sad, silly, angry, or scared and that one shouldn't bottle up feelings inside. Some young readers may even be inspired to start their own sketchbook.