I made a top-10 list of speculative fiction recently and I noticed something funny: Most of it is science fiction.
It's funny to me because I rarely write science fiction. I write fantasy to avoid having to justify why the world fits together the way it does. I can just write imagery. The result rarely feels satisfying.
I think part of what's missing is rationale. In listening to Too Like the Lightning, one thing that strikes me is how their world fits together in an explicitly rational way. Their weird norms make a certain amount of sense. They seem to come from carrying principles to logical extremes. Like, Cartesian mind-body dualism, and engaging with people first as minds and only second as bodies. I think this is part of what I like about Worth the Candle, too: Things frequently fit together in a way that the characters themselves understand and explain.
Could there be substitutes? A society doesn't have to be rational. They rarely are. How could fantasy be interesting without rationale? Maybe what I'm looking for is less a society that follows a logical scheme and more a sense that people have thoughts and ideas and feelings not dictated by their role in society or by contrivance but by serious engagement.
And now that I think of it, Buddhism for Vampires seems pretty close to what I might ideally want in a non-rational fantasy story. The protagonist, Surya, is born an outcast, but a loved one, until his mother dies. After his mother dies, his mother-in-law uses their culture as a club to beat him, which he resents. And he sees the adults around disobeying the Five Precepts (the moral laws of their village's religion) when it suits them, and furthermore debating what counts as following vs. not following the Precepts. Those three threads come together such that Surya starts to question the culture around him—not all at once but piece by piece.
It might be relevant that Buddhism for Vampires is set on Earth, in (I think 8th century) India. Many of my favorite speculative fiction stories are also set in our universe in the far future, or variations of our universe.
But I wonder if that's the whole story. I don't read a lot of vampire stories and I don't expect I'd like them more than general fantasy stories. Also, I love Worth the Candle and A Practical Guide to Evil even though the former's world and story is only tangentially connected to our universe and the latter is not obviously connected at all except thematically.
It strikes me that something Buddhism for Vampires, A Practical Guide to Evil, and Worth the Candle have in common is something like questioning received wisdom. That includes ideology, norms, and ways of doing things. In part, they're about about seriously struggling with the question of what if they're right, what if the received wisdom is right and I'm wrong, but also—once the norms are rejected—about the struggle to overcome the emotional reactions and habitual patterns that come along with those norms. And, to the extent the received wisdom was correct, dealing with and understanding the consequences. Maybe that's what I like about fantasy when I like fantasy.