3.5 maybe. This series is a little frustrating. Beautifully written, the prose simply drips like honey. It's the world building that is the problem. It's similar to how I felt about Divergent (the first book anyway) in that I get this is how these characters would act, how they would be, in this sort of situation. It's just that I can't buy into the situation. I'm not a scientist, but I know enough to know that the science is really sketchy, and the way the plot about the "virus" resolves didn't feel earned or properly set up. It didn't make sense really at all. However, I meant what I said about the writing. I can forgive A LOT when it is couched in such lush prose. And I must admit that I couldn't put this one down. I may not buy into the world, but I came to really feel the characters. The pacing was much better than in the second one, and I have hopes for Lauren DeStefano's future books.