Memory Boy by Will Weaver

Ash is still falling from the sky two years after a series of globally devastating volcanic eruptions. Sunlight is as scarce as food, and cities are becoming increasingly violent as people loot and kill in order to maintain their existence. Sixteen-year-old Miles Newell knows that the only chance his family has of surviving is to escape from their Minneapolis suburban home to their cabin in the woods, As the Newells travel the highways on Miles' supreme invention, the Ali Princess, they have high hopes for safety and peace. But as they venture deeper into the wilderness, they begin to realize that it's not only city folk who have changed for the worse.