The Passage by Justin Cronin.
Reading this book was a departure for the kind of book I typically read, and I was more than pleasantly surprised. Cronin writes in the vein of Stephen King and others who weave huge, dark tapestries of apocalyptic events. This novel was actually written for and with input from Cronin's daughter who told her dad that she wanted him to write a book about a young girl who saves the world. It's mysterious and terrifying and a real page-turner. For anyone who loves to sink their teeth into a juicy thriller, this is just the ticket.