The Knight (Wizard Knight Series #1)

A young man in his teens is transported from our world to a magical realm that contains seven levels of reality. Very quickly transformed by magic into a grown man of heroic proportions, he takes the name Able and sets out on a quest to find the sword that has been promised to him, a sword he will get from a dragon, the one very special blade that will help him fulfill his life ambition to become a knight and a true hero.
Inside, however, Able remains a boy, and he must grow in every sense ...