Incarnations of Immortality by Piers Anthony
This is a very interesting, thought provoking series. It shows what happens when normal people(except for the fact that they are living in a magical world) take on the roles of various incarnations. It is very interesting to see how they act, and how the character evolves throughout the storyline.
Also, there is a pretty well done plot to each of them, and how he writes the character's strengths and weaknesses. One thing I wasn't too impressed about was how all the major characters of all the seven stories are related or connected somehow, as if the incarnations are all chosen from one large family. Still, the series is a very good one worth reading!