[Shannara 06 - The Word and The Void 00b] - Imaginary Friends

Jack McCall is
ten days shy of his thirteenth birthday, a happy kid with wonderful
parents, a great best friend, and a bright future. But after a series of
headaches forces him to visit the family doctor, Jack discovers a dark
secret about himself, one that threatens to destroy him.All is
not lost though. In mysterious Sinnissippi Park where he is banned to
tread, Jack discovers unexpected help from the most unlikely of friends
and begins a quest to locate the most potent of magics -- one he needs
if he is to survive.