Let's start with the good. Ngan's prose is absolutely magical. I was constantly stunned by her poetic voice and masterful wordcraft from the first page to the last. Her descriptions of the world around Lei are so engrossing, I could almost feel the rain on my skin. Really really fantastic. She also tackles some major issues in this book, first being the caste system and the debilitating prejudices that keep Paper (humans) trapped in lives of squalor and fear. After that, Lei is brought face-to-face with the reality of slavery, having been kidnapped and gifted into servitude herself. Not only that, but the nature of her indenture is equally repulsive, made all the more horrible by the fact that so many people around her keep telling her how lucky she is to be a Paper Girl. All of these are big ideas to tackle, and Ngan does a reasonable job of it. She also brushes up against the gray morality of taking life to save life, but doesn't really invest.
The good is also somewhat aligned with the bad in this case for me. While elegant and lush, the prose began to bore me after about 100 pages. I stopped caring about the scenery and started hoping something would happen. This book dragged for me. The physical styling of the demons was too 'furry'-esque for my liking. Lei also felt a bit one-dimensional, as did the rest of the characters, and I couldn't quite get attached to any of them. The romance was sweet and understated, just about right for a young-adult novel in my opinion. In the end, though, I won't be reading the sequel to this. I just don't care what happens to Lei next.