A very funny little book about a fairy and the family she elects to live with after they confess they believe in her. On a perfectly normal Sunday, as Caroline and her parents are motoring off to the Natural History Museum, a fairy who calls herself Hilary suddenly appears and asks to join them. She joins the family, too, looking like an ordinary child and behaving like one, at least until Caroline coaxes her into a little fairy magic. She gives the family cat, King Arthur, the power to talk, and makes him invisible so he can go to school with the girls. Her magic makes Halloween a little more wondrous, and helps the girls construct the biggest snowman ever. When they’re invited to a birthday party that features a lame magician, Hilary give him a hand, secretly, and he outperforms himself. A dour plane trip turns into a glorious one with Hilary’s aid, while her work in Caroline’s mother’s garden makes other gardeners jealous. In her wonderful frolic, Strauss mingles ordinary events and enchantment with ease; the fun is complemented by charmingly droll black-and-white drawings. (Fiction. 7-11)