This is a terrific science fiction adventure story with a heart.
Moon doesn't know what he is. He's been trying to live with other people, but they don't look like him (most of the various races in this world are physically different from each other), and unlike them, he can shift into another shape, one with wings, a fact he conceals because the winged shape looks something like the Fell, an evil race bent on conquering and consuming the other races. When his secret is revealed, Moon must not only discover who he is and his new place in the world, but he must strive to help his people, the Raksuran, deal with the Fell, who have been pursuing him for longer than he realizes.
As you can see from my summary, the book presents great internal and external conflicts. One of the things I appreciated most is that it's science fiction with nifty skiffy ideas, but it doesn't sacrifice characterization (internal) for the development of the ideas (external), as so much SF does. The external story, the adventure and peril involved in dealing with the Fell, is perfectly balanced by Moon's internal story--one of my favorite tropes, the lonely person finding his/her place in the world story.
That said, some of the secondary characters felt a little indistinguishable to me--the death of one of them near the end left me unmoved--but the main characters, Moon, Jade, Stone, and Pearl--are deftly realized, their stories gripping. Moon's predicament is particularly compelling. I was interested in the social structure of both the world, in which various races coexist, and of Moon's people, who are ruled by queens. The relationship between the sexes here is alien, and really interesting. Not exactly matriarchal, but something else. The real star here is the land, the Three Worlds, which is full of variegated peoples and landscapes and which demands further exploration; it's a world I want to return to. Moon and his people are wicked cool, sort-of human-looking, but who can shift into other creatures, some of which have wings and which I persisted in imagining as dragon-like. There are some great battle scenes with vivid action.
I read a review copy of this, but will for sure seek out the actual book once it's published, because it will reward re-reading. Highly recommended!