The Cerulean

Cerulean tells the story from two points of view. One group is a society of feminine creatures that are in a city in the sky. They marry in groups of three "mothers" and then one has a child. The other group is more standard humans. Their society is male dominated. 

Sera is sent down from the sky city as a sacrifice to "unteather" the city.  However, she does not die. She ends up getting caught by a human. The humans discover that her blood can cure wounds. They keep her as a way to cure.

Some members of the sky city have a crisis of faith as the sacrifice did not work as it should. People on the lower world also have their conflicts. The children of a key figure are set to support Sera and leave the area. They end up connecting at the end.

I kept feeling that this was a story about fairies. It is a set of two interesting cultures that have their own struggles, and even more challenges when meeting together.