Them

Them is the third book in the Remnants series by K.A. Applegate.

Back Cover Summary
The world we know as Earth is dead. Jobs, 2Face, Mo'Steel, and the other survivors had hoped to find a place capable of sustaining human life. A place where they might start over. A place they could call home.

But the land they found is not actually a planet at all. It's a ship. A ship capable of replicating both human life and existence – but not to a believable extent. The survivors of the Mayflower Project have begun to believe that who or what ever created this place is playing games with them. Deadly games. And the difference between winning and losing could mean the difference between life ... and death.