Three sisters travel to Oakland, California, from Brooklyn to visit their mother, whom they haven't seen since she left them and their father some years earlier. The year is 1968 and the girls spend their days at a summmer camp sponsored by the Black Panthers. Talk about a great premise! The book starts kind of slowly. The first half establishes the characters and the milieu, but it's not terribly exciting. The plot kicks in in the second half of the book, however, and the last few chapters are just phenomenal. It becomes clear why the somewhat slow build-up to the final scenes was necessary.
One Crazy Summer was written for grades 4-6. I'd say most kids this age will have no idea who Booby Seale and Huey Newton were. The book infuses details about the Panthers into the story in such a way that I think kids can pick up quite a bit about the Black Panther movement and the era in general. There's also a segue in the story where the characters visit San Francisco and get to see real live hippies (they'd previously only seen pictures in magazines).
This story is fiction, but it feels incredibly true to the time and place of the setting. This is an excellent read for kids, and there's a lot for adults to appreciate in this book as well.
More info about the Black Panther Party can be found at Wikipedia.