Maze Runner (9781909489400) by James Dashner

When Thomas arrives in the Glade, a walled encampment at the centre of a bizarre maze, all he remembers is his first name. But he's not alone. Like Thomas, the Gladers don't know why they're there, or what's happened to the world outside. All they know is that every morning when the walls slide back, they will risk everything to find out.