In his debut as a picture-book illustrator, fine artist Palmer depicts a young black boy with a crown of dreadlocks atop his head and a big imagination. He’s convinced that a dragon in his closet is responsible for various happenings (leaving a dollar bill under his pillow when he loses a tooth, tidying his room while he’s out) and also for the mischief he’s blamed for (tracking mud in the house, breaking a flower pot, eating all the cookies in the jar). He tells his parents about the dragon at the beginning of the book, but after the cookie incident, his exasperated mother leads him to his closet—where they...