I have only read the first chapter, but anything that makes me go "Yes! So cool!" is starting off on the right foot :D

EDIT: Okay, a bit in - if you are particularly sensitive to Mary-Litigation, this does tread near that territory - Harry is well-characterized and interesting, but becomes a clearly supporting character, with our D&D planar expatriate winning the Initiative roll on all of the plans. On the other hand, you might simply call it munchkining.