When Simon's proper and stuffy relatives come to stay for spring vacation, his mother packs him off to the country to stay with Aunt Matilda and Uncle Philbert. Simon's not sure he wants to go. When people talk about Aunt Matilda, they raise their eyebrows and say, ""Isn't she sort of. . . you know?"" Simon has to fill in the blanks himself, and wonders if his great-aunt is a coldhearted child-hater. Actually, she's nothing worse than the owner of a trio of llamas, a 1946 New York taxi cab, and two horses saved from a glue factory. Both she and her husband, ""the rudest man in the world,"" are bent on tearing down the rules of convention and propriety. They serve Simon pizza for breakfast and pie for supper, and start right in on his ""un-lessons,' teaching him how to burp, spit, and play tunes with his armpit. Reminiscent of Betty MacDonald's stories of Mrs. Piggle-Wiggle, this is rollicking good fun, with much of the drollery captured in Smith's black-and white illustrations. MacDonald (Cousin Ruth's Tooth, p. 230, etc.) limns a satisfying conversion of Simon from goody-goody to a boy who won't take any guff. Sharp characterizations and crack dialogue will have readers laughing out loud.