Gray: Part II

A dense black cloud boiled up in the southeastern sky. It rose high and fast, like a time-lapse movie of the birth of a thunderhead. But it was no rain cloud. Wholly black, it reached up and up until it loomed over her, blocking out the sun. Somehow, she knew, it was Death coming for her.

Three months have passed since the mysterious event transformed life on Earth. The air grows colder, the days shorter, the snow deeper, and Coral and Benjamin struggle to find food enough to keep them on their feet. Moving on to warmer climes seems their only long-term hope, but travel means a terrible danger: encountering other people. The rule of law is gone, the old morality is crumbling, and Coral needs all her wits and skill to survive in this brutish new world.

(Gray is a trilogy, and it's best to read it in order.)