The Maze Runner by James Dashner

Thomas remembers nothing but his name. Awakening in the lift to the sound of the doors cranking open, he finds himself in a glade with other boys. A maze without end, the Glade is merciless and no one knows why they are there or how they got there. It changes every time they are there and there are the grievers to fear, cruel metallic creatures which will reduce the boys to shred should they come near. The boys try again and again to brave the Glade without succeeding. That is when a girl arrives with a message that will drive ice through their spines when they hear it.