I also liked how the question of souls was dealt with, as it was never in question at the start of the book, but became an obvious issue at the end, with the "normal" people questioning the students' humanity because of what they were created to do. It made sense that people would prefer to believe that the students were not fully human, or else using them as organ banks would seem ... well ... inhuman, which it was. Treating them as less than human while harvesting their organs was even worse.
At any rate, it's a good book. Most of my assumptions about what was going on were accurate, so the clues were obviously well-written.
Now I don't know what to read next.