Babylon Falling. Dustborn Chronicles, #1

In the shattered lands beyond the last great city, hunters take contracts no one else will touch. Kiera was bred for survival on Mars and forged in the wastelands of Earth. She kills what stalks the roads, finds what others lose, and asks no questions she doesn't need answered. Then a child disappears. Tracking him pulls Kiera through broken settlements, forgotten corridors, and the edge of a city that should not still function.
What waits there is older, larger, and far more organised than the raiders and beasts she knows how to fight. To bring the boy home, Kiera will have to face the one thing she cannot hunt: a system built to survive everyone inside it.