The Young World (The Young World Trilogy)
Welcome to New York, a city ruled by teens.
After a mysterious Sickness wipes out the rest of the population, the young survivors assemble into tightly run tribes. Jefferson, the reluctant leader of the Washington Square tribe, and Donna, the girl he's secretly in love with, have carved out a precarious existence among the chaos. But when another tribe member discovers a clue that may hold the cure to the Sickness, five teens set out on a life-altering road trip to save humankind.
The tribe exchanges gunfire with enemy gangs, escapes cults and militias, braves the wilds of the subway and Central Park . . . and discovers truths they could never have imagined.