Dark Places by Gillian Flynn

This book has you guessing the whole way through about the murders that took place in the Day home 20 years ago.
Libby is the sole survivor, besides her brother, Ben, of a murder that took her mother and two sisters 20 years ago. Her brother, Ben, was jailed for the murders and little Libby, at 7 years old, was one of the reasons for his conviction. 
Libby has lived with her aunt Diane, as a little girl, then has been on her own, living off the "fame" of being the one who survived. That money is coming to an end and she is contacted by a group of people who are convinced that Ben did not commit the acts.
They agree to pay her to go talk to some of the people who were involved with the family in the past, including her father, Ben's girlfriend, Diondra, his friend Trey, etc.
Gillian Flynn leaves you guessing right up until the last chapters about the real happenings that night and it is scary to read.

http://gillian-flynn.com/