Don't let this being categorized as YA fool you, I'm a full-grown adult and this book TERRIFIED me. I'm also a self-proclaimed "indoorsy" type, and this story didn't make me want to change that anytime soon. The story starts out relatively mildly- two girls head out for a short backpacking trip before the start of college, and at first it seems like the biggest issues are going to be the way the wilderness tests their friendship. The seams are already coming apart when the real problems begin. Underneath the horror are good things to say about friendship and trust and the dangers out there in the world. The book is relatively short, but honestly I was grateful for that because these characters did not need to be put through more than they already did in this story. Stephanie Perkins has been an author I've consistently enjoyed, and this is definitely at her best.