Celestis

Paul Park's world of Celestis is not as dark and brooding as that of Paradise in his Sugar Rain books, but the story is even more disturbing. Humans have subjugated the planet's native aboriginals in those ways that humans often do. On the surface, all is calm and civilized: aboriginals appear happy with the lifestyle change, the cultural opportunities now available, and a victory over another native race that had enslaved them for centuries. But the calm is only a veneer that hides the decay and anger beneath, a short-term peace.
Park details the worms of decay through his description of Katherine, the daughter of a wealthy, Westernized native merchant. Katherine is a devout Catholic and takes drugs and undergoes periodic plastic surgery to make her more human; with her transplanted knucklebones, she can even play Beethoven on her concert piano. Katherine and Simon, a young diplomat assigned to Celestis, are thrown together when they're kidnapped during an uprising. Simon falls in love with her, but Katherine, cut off from the medication she needs to keep her humanlike, begins to revert to her natural--though to her quite unnatural--alien state.

A tangled predicament of violence, transformation, and loss, Celestis delivers an eerie view of history, psychology, and the perception of others.