Fletcher (Crystals of Memory, #1)

As he lay dying, the mind of an old historian is placed in a magical crystal by an old friend. Over a thousand years later he wakes, in the shared body of a young boy, who needs him to save his life.

The problem is that a disciplined old man has very different ideas about how to live a life than an adventourous, but lazy, boy.

Worse, an ancient war is upon them, a thing that will alter the course of both their lives, forever.