This book from Gillian Flynn was published before Gone Girl but I've just now got around to checking it out. When the main character, Libby, was seven her mother and two older sisters were brutally murdered in their rural Kansas home. Libby managed to escape. Her teenage brother was convicted of the crime, largely on Libby's eyewitness testimony.
Fast forward 25 years. Libby is now a very messed up adult. She's not the most likable of characters, but I found myself mostly sympathetic toward her anyway, given what her life had been like. She answers a curiosity seeker's letter and thus heads down a twisting path to discover/remember what really happened on that terrible night.
I found the mystery interesting, though occasionally unbelievable. I also liked that the ending was at least somewhat optimistic. Flynn knows how to write deeply flawed characters that pull you in.
Warning: the description of the murders is graphic and there is a scene involving animal abuse that I had to entirely skip over.