Polymorph (1997)

Backcover Synopsis: Lee can change her gender and ethnicity at will, allowing her to slip freely through New York society. She thought she was the only “polymorph” … until a chance encounter with another of her kind.

The first third explores some interesting issues regarding identity, but later it the story changes into an adventure plot. I thought it would have been more interesting if Westerfeld had just explored the whole concept of identity in combination with shapeshifters more, but adventure is also okay in my book. But then we got the ending. I really, really hate “horror” endings. You know, the kind where when the good side has won, we either see that the evil has survived or the good guys have been infected with the evil and we just know they will transform into what they have fought during the whole story (even if I misread the ending, that’s how I saw it). Like I said, I really hate this, it makes me go sour on the whole book (like reading a bad sequel to a good book).