So This Is How It Ends — Tui T. Sutherland

The end of the world is only the beginning

From New York to Los Angeles, Chile to Egypt, five teens awake to find their cities eerily deserted. Why have they survived when so many others haven't? What force connects them to one another? Moving north, south, east, and west, they are pulled together to fight the ultimate battle in a war they never knew about -- a war that has been raging since the dawn of time.