The Chosen (Contender, #1) by Taran Matharu

Introducing an epic new trilogy from Taran Matharu, author of the New York Times–bestselling Summoner series.

Throughout history, people have vanished with no explanation. A group of teenagers are about to discover why.

Cade is in a "therapeutic" school, contemplating his future, when he finds himself transported to another realm. He soon discovers their new world is populated with lost remnants from the past: prehistoric creatures, ancient relics, and stranger still — people. Overwhelmed by his new surroundings, Cade has little time to adjust, for soon he and his fellow classmates are forced to become contenders in a brutal game, controlled by mysterious overlords.

But who are these beings and why did they choose these teens? Cade must prepare for battle . . . because hiding is not an option.