I feel like the author was trying to say something about Beauty and Ugly, but failed to do it well. I suffered through the story and felt bad for the protagonist, hoping for a triumphant ending with a realization of self worth. There wasn't. The ending wasn't necessarily sad, but I was left feeling unfulfilled. I don't recommend this book.
I read this when I was 12 or so, and I just re-read it. Essentially the story is about a girl who goes to a summer camp where at the end, a girl is picked from every cabin to be a "bathing beauty" and a "bathing ugly". Out of all the bathing beauties, the prettiest is picked, and the goofiest costume is picked for the "bathing uglies". The main character decides to lose weight by not eating candy anymore and by eating vegetables so that she can try to be a bathing beauty. The idea of being sent to a camp where superficial qualities like looks determine your status at the end is horrifying. Weird and sad.