Bummer Summer (Vintage Paperback) by Ann M. Martin

What a bummer!

Summer is supposed to be the best time of the year. But this summer looks like a total loss to Kammy Whitlock. First, her Dad gets married again. Then his new wife Kate moves in, and Kammy has to put up with her two children. They won't leave Kammy alone! Three-year-old Muffin flushes Kammy's best paints down the toilet, almost strangles her cat, and the baby cries for hours at a time.

Camp has always sounded hateful. But when Dad and Kate suggest that Kammy go away to Camp Arrowhead, Kammy figures it can't be worse than staying home. How wrong can a person be? Arrowhead is a disaster. Now the only question is: what can Kammy do to save the summer from being a total bummer?