What aspects do you enjoy most about your favorite sci fi or fantasy novels? Obviously it’s a mix of everything but what consistent themes do you find yourself returning to frequently?

To give an example, I tend to like complex and internally consistent magic systems or “hard magic” systems, eg Brandon Sanderson. He basically invents an alternative physics in a given series and there’s a whole set of stories around that.

I also put a lot of weight on complex characters, eg Game of Thrones. You know it’s good writing when someone can push a kid out of a window in the first episode and then somehow kind of make you almost like the guy later on.

If you don’t like sci fi and/or fantasy, what is it about the genre(s) that you dislike? And do you like one but not the other, or both or neither?