I'd give this book like a 4.75. 
 Libby Day was the sole survivor of her families massacre. Her brother killed her mother and two sisters. Libby has spent the last 24 years living off donations from well wishers but now the money has almost run out. She's approached by a 'kill club' to reinvestigate the case, desperate for money she takes the job. The story is told from Libby's point of view now and Ben and Patty's point of view the day of the murders. 
 I really enjoyed this story. I enjoyed the way the mystery unfolds and how great the characters are. The characters all have flaws but are realized humans. And a lot of them are likeable characters, unlike Gone Girl where everyone was fucking crazy and despicable. This book would have been 5 stars for me but the pacing was a little off in places, so I'd give it like 4.75. 
 Audio book note: this book has multiple readers for the different points of views which I really enjoy. The only thing I'd was slight of was that Ben's reader seemed a little old for 15.