Cooney's gifts for humor and characterization are well blended here as a thoughtful teen-ager faces a get-together with her uniquely blended family. Shelley, 14, has a thrice-married father; her mother (Dad's second wife) lives with her new husband in Paris. Shelley and her younger brother, Angus, are spending the summer with Dad and his third wife when they are all invited to his sister's 20th anniversary celebration. Since that branch of the family has well earned its derogatory name, ""The Perfects,"" Shelley and her insecure stepmother view this upcoming event with alarm; but Shelley faces the trip with fascination as well as dread, hoping to find out some truths about her father--and about whether she has an older half-brother. What happens, of course, is that Shelley confronts some uncomfortable revelations about herself and the way she has perceived others. Shelley narrates with warmth and understanding, maturing believably from wisecracking skeptic to maturing adolescent with glimmers of compassion. Her family is limned with deft, witty strokes, developing and growing on the reader as the story progresses. A realistic, sometimes hilarious picture of modern family life.