Cross multiple personality, extra temporal dimensions, a D&D gaming world developed by an 11-year-old, past life regression, all stirred together by a skilled "urban punk" sci-fi writer. It reads quite fast, and is a good choice for a teen who enjoys sci-fi as well as for adults.
Interesting exploration of alternate timelines for one character. We see him in four different versions, each with a distict personality, each in his own alternate universe. In the end, only one can survive.