First of all, it's very different from any other novel I've read. The idea is very unique. Secondly, it's written from Cassel's POV, a male POV, something we don't get a lot of. And third, there were so many twists and turns that just when you think you have it figured out, you find out you're wrong. I hate when you figure out the ending in the beginning, and that was definitely not the case with this one. You don't know who to like or who's doing what. And even Cassel, our narrator, keeps things from us.
I can't wait until book two comes out. Unfortunately, it's probably at least a year away.