I know I just said SciFi is really hard to write, but Fantasy is too. Not quite as hard, I think, but still pretty difficult. The fact that you get to design a world can make it much harder than “regular” fiction.
The problem is that Fantasy stories still have to been internally consistent.
If you’re writing something that’s set in the “real” world, you already know all the rules: you’ve lived with them your whole life. The physics is determined. You have lots of reference materials for different cultures, governments, history, etc.
In a Fantasy world, you don’t have the reference materials. Or if you do, as in “Urban Fantasy” set in real-world cities, you mess it up by introducing a magical element. And those fantastic changes, even if small, have dramatic effects on the nature of the world.
For example, I once tried to design a “simple” magic system in which the magic user had telekinetic powers. That’s all. And nothing super-powerful, either: he or she couldn’t raise a sunken spaceship from a murky swamp or anything. But the effect was far-reaching: the person became instantly and exceptionally dangerous. If you can move anything nearby with your mind, it would be pretty simple to become a weapon (I’m reminded of the Coinshot in the Mistborn series). Or forget the makeshift bullets – just move a tiny part of a foe’s brain, without moving the rest of their body accordingly. Dead.
And that’s always bothered me about magic systems. There is almost always an easy way to use it in an extreme fashion to take over the whole world.
So my telekinetic sorcerer doesn’t exist. Maybe I should have started with the character and plot without thinking about the magic system, but the magic was the part I was most interested in.
I also wrote a short story in which the protagonist was learning about magic, and the boundaries were unclear. And as I introduced the effects of the magic (one person hadn’t aged in a long time, for example), I realized that I didn’t know how it worked, and that was a problem. What were the boundaries, and were they different for each magic user?
I also considered how prevalent the magic was – could anyone use it? Was it equally powerful for everyone? Did the magic have the same nature for every user, or did each person access it differently (as in the elemental styles we’ve all read about)?
And working through those questions, I recall how in many, many fantasy series, the magic-wielding character (of any experience level) becomes exponentially more proficient as time passes. Even the characters who are supposedly expert users at the beginning of the story make choices which seem quite novice in the context of the understanding the reader develops later. “Why didn’t he just do X at the beginning?” I often find myself asking later, once the nature of the magic is known. I fear it’s because the author wrote the beginning of the story before discovering all that the magic could do, before considering all of the ramifications of his or her choices.
So Fantasy is really hard to write also, and giant kudos to the authors who are good at it, because they are awesome.