Grams, Her Boyfriend, My Family, and Me

``I have a theory about families. The less you get involved, the less trouble you get into,'' begins this sparkling novel. Narrator Andy, 15, has led a trouble-free existence by dint of his total self-absorption. But big changes rumble through his family when his mother gets a job. Andy not only has to do household chores, but must take turns with his two teenage sisters in baby-sitting their six-year-old twin sisters--duties he shirks as much as possible. Even more of a disruption, Grams, Andy's bossy paternal grandmother, moves into the Hallidays' too-small house and tries to run it her way. The tension mounts between Ma and Grams until Grams announces that she's going to marry Harry, whom she meets after she hits him with her car. But with Andy's father and Harry's overbearing daughter dead-set against it, the marriage seems doomed. Despite himself, Andy haltingly demonstrates that he's at last on his way to being ``a caring kind of guy.'' Derby ( Goodbye Emily, Hello ) has concocted a real treat, imbued with warmth and sly perspicacity. Andy's fresh and lively voice will captivate readers until the last page. Ages 12-up. (Jan.)