The final book of a remarkable and engaging trilogy. I liked this book the least, it suffers a little bit from 3rd book syndrome (where the author tries to explain everything and then either doesnt convince or leaves too many unexplained holes, leaving me feeling like it would be better just to not even bother trying). 
 The ending is perhaps a little too emotionally satisfying, I would have liked it to end with (view spoiler)[ with them walking out of the silo, not knowing if they would make it or not (hide spoiler)]. 
 I feel like I am being a bit picky here so I will just add that as an overall series I loved the premise, the characters, the strong female lead, the pacing and the format of the books and the order in which they were written. These are great dystopian books.