We Were Liars, By E. Lockhart

It's about a wealthy family living on a private island during the summer. The "liars" are 4 cousins and they do something bad. The main girl, Cadence, loses her memory of the summer when the accident happened and, through the course of the book, she is trying to figure out what happened. You don't find out until the very end...and it's very screwed up. It threw me off, which I like, and the book kept me engaged. I couldn't put it down! Easy read but very worth it.