Acadia. Children of Acadia, #1

Two hundred years ago, the Roaches swept across the Earth, annihilating everything in their path. Humanity's survivors retreated behind the walls of Acadia, a militarized city where every citizen's worth is measured by a ruthless merit score. Earn enough points, and you live in safety. Fall short, and you're Rifted-cast into the depths beyond salvation. Jessica is a girl on the edge of that fate, forced into the Mahghetto-an unforgiving gauntlet where failure is fatal.
Cojax is a young soldier from the city's lower tiers, desperate to prove himself in a society that sees him as expendable. When a strange presence is discovered beyond the Wall, the two are thrust into a conspiracy that could topple Acadia's rigid order and ignite a war it cannot win. In Acadia, loyalty is rewarded. until the day it kills you.