Jellicoe Road by Melina Marchetta
In this Australian import, Taylor is the reluctant leader of the Jellicoe School’s boarding students’ territory war against the Townies and the Cadets. She’s not that interested in the war, partly because she ran off with one of the cadets a few years ago, but mostly because she wants to solve the mystery of who she is. When she begins to find clues that tie her to a terrible auto accident that happened before she was born, she is obsessed with the three teens who alone survived the accident that killed all other family members and the teen that saved them. A cadet becomes the fifth member of the close friendships from years ago. Now Taylor knows she is part of it, and the territory wars had their beginning with those five friends.