Z For Zachariah by Robert c. O'Brien

For those of you who loved the strong heroine of the Hunger Games, this is a must read. Also set in the future where those adults messed up the world, Ann Burden believes she is the only one left. It was always said the valley she lived in with her family had its own environment. No matter what happened to rest of the world, it kept everyone safe that lived there. But when her family and the others left to find help, they never came back. She was left behind just in case the telephones started working again. With only her brother's dog to keep her company, Ann found a way to stay alive, but she kept a look out for any strangers that might have made it through. One day she saw smoke from a fire and each day that smoke came closer. Ann quickly planned how to stay safe, but did she really need to? Who is this stranger and how did he survive? The chilling answers test her survival skills and make her finally realize that the dog must die.  What would drive her to doing that to the one living being who has helped keep her sane? Would you do the same? Would you?