Chosen (Lost Books #1) by Ted Dekker

Think with your heart and prepare to die for you have been chosen.

The land of the Forest Dwellers has been decimated by the Horde under the watchful eye of the vilest of all creatures, Teeleh. Thomas Hunter, supreme commander of the Forest Guard, is forced to lower the recruitment age of his army from 18 to 16. From among thousands, four new recruits are chosen to lead--and perhaps die--for the greater good.

The chosen four are sent on a quest to prove their character, but their mission takes a dramatic turn when they are intercepted, sworn to secrecy, and redirected to a different endgame. Now they must find the seven lost Books of History. Books that have power over the past, present, and future. Books whose words are alive. Books sought by the Dark One that control not only the destiny of their world...but that of ours as well.