Even in the here-and-now, twelve-year-old Kammy's instant family is a mite unusual: her economies prof dad, a widower since Kammy was four, has fallen in love with and quickly married biology prof Kate, who has a three-year-old daughter, yuckily called Muffin, and an as-yet-unnamed, two-month-old Baby Boy. (The romance flourished after pregnant Kate was abandoned by her husband.) But granting those oddities, new-author Martin has made Kammy's situation empathic and unagonized. The first post-marital days are a disaster, with disorderly Kate and her tots (Muffin is a cajoler, Baby Boy has colic) wrecking all the small domestic rituals dear to Kammy and her father. But Kate is not obtuse, and Kammy's peace-loving dad does recognize her dilemma-so a compromise is achieved: Kammy will try two weeks of summer camp, for which she has no inclination, to let things settle out. Happily, she has an ideal counselor in Nancy--""attractive but not cute""--and an outgoing bunkmate in Emily, who's ""really nice. And fun."" Unhappily, she can't bring herself to undress in front of the other girls; though a super swimmer, she's terrified of snakes in the lake; and she's also panicked by the idea of waiting table. But one way or another, these problems get taken care of (not solved). And having met and conquered camp, Kammy doesn't have to go home when the two weeks are up: she knows, besides, she's not unwanted. A strong heroine with weaknesses to scale, in a deftly turned problem story.