I read a good book a while ago and can't remember the title.
It is the story of people stuck on a planet made of hexagons, where the level of technology is set depending on the type of hexagon. Some have high-level tech, others have magic, and some have both or neither. Magic can't be used on tech-only hexagons, and vice versa.
I also remember that at some point the heroes get captured by a magical tribe, and one of the women ends up being forced to touch a pyramid that transforms her partly into a donkey.
I also think that the planet was alien-made, and the hero ends up realising that he is not human at all but alien. He is just so old that he forgot part of his memory.
I don't think I mixed up two different books in there, but I might have...