I'm a Harry Turtledove fan, and am willing to overlook a lot of flaws in his writing if the basic idea is fun or intriguing. But a novel with a one-dimensionally insufferable character whose transformation makes him one-dimensionally selfish violent and cruel just won't work magic. The religious system (Zoroasterian or Manichee) where 2 one-dimensional gods battle it out could have been treated imaginatively, but this never got off the ground either.