This is a book about a child's will to survive in the face of horrible abuse. Throughout the book I kept hoping that Libby would be caught and taken away- her treatment of Carrie is criminal. The book is billed as a possible stand-alone read. Certainly it's possible to dive in and understand what is necessary to appreciate this book. Still, this is a follow-up to Flock's Me and Emma, and the premise of the entire plot gives away what I suspect is the crux of the first book. I haven't read Me and Emma, but I suspect the plot of What Happened to My Sister relies on some major spoilers.
Elizabeth Flock, What Happened to My Sister (Ballantine, 2012) ISBN: 0345524438