There's a supervolcano underneath Yellowstone, and in this story, that volcano explodes and covers much of the United States in a layer of ash, plunging the world into darkness and chaos. Much of the world's food supply is ruined, and anarchy follows as people attempt to survive in a world that has changed dramatically.
Wow. There has been an explosion of dystopian and post-apocalyptic literature in the wake of The Hunger Games. As is true with many things, 90% of what has been published is crap. This book is in the other 10%. I started it at 9 PM after working on homework all evening. Before I knew it, it was nearly midnight and my eyes could barely stay open, but I was 325 pages into this book and couldn't imagine putting it down.
The characters in this story were believable, the situation they were in was realistic, and there were just enough calm pauses between the catastrophes to keep hope alive and to allow the adrenaline rush to settle down a bit.
I'm almost afraid to pick up the sequel, because I'm not sure it can top this book. This one was amazing. If you haven't read it yet, you need to.