For all the tweens who that believe in BFF but find out, to their great disappointment, that it isn’t for everyone, this is the book for them. Jemma’s best friend Tammy moved away at the beginning of fifth grade but they agreed to spend the following summer together at camp. Unfortunately—and unexpectedly—Tammy arrives with her possessive cousin Brooke, whose parents are caught up in a messy divorce. The only one who can’t spot Tammy’s altered loyalty is Jemma, who is convinced that she can somehow win back her straying friend. As a counterpoint to Brooke’s unpleasant attitude, vanilla-flavored Delaney becomes the always-loyal new friend, who unrealistically bounces back after Jemma’s rejections whenever Tammy seems like a better prospect. The emotional turmoil plays out against a lovingly depicted month at summer camp, as Jemma tries and fails, repeatedly, to learn to water ski but shows a nice talent for sailing. Though few children actually get to attend a full month of summer camp, many others will enjoy it vicariously through this somewhat superficial effort. (Fiction. 8 & up)