Between 2008 and 2009, Ted Dekker released six novels aimed at young adults that made up the Lost Books, the last two of which were co-written with Kaci Hill.
On August 24, 2010, the collection became available as this box set.
Lost Books Box Set book description
Thomas Hunter handpicks four teens to help protect the Circle against the evil Horde.
But when six all-powerful books suddenly disappear, these teens secretly abandon their original mission and travel across two worlds to recover the books and discover their destiny.