Dark Places by Gillian Flynn.
This is one of the best books I have read in a while. I finished it in 2 days-I couldn't put it down!
A girl's family is slaughtered, and she fingers her 15 year old brother as the murderer. She then meets a group of people who not only make her question her original testimony (which she was kind of already doing), but leads her on a search for the truth.
I was really touched by this book, by the many paths a persons life can take, and how one decision can change everything.
I will warn you-there a few graphic scenes, not only when the family gets murdered but when some cattle are killed as well. I basically skipped those paragraphs.
An excellent book, I highly recommend it.