Overall, a strong end to a good series. I had my qualms, reading the middle book, but Oliver has redeemed the series, allowing me to recommend it to friends without feeling bad about it. 
 One serious problem I ran into. I couldn't remember anything about Pandemonium. Seriously, I almost started to doubt that I had read it. I'm not sure if it's just that too much time had passed, or that I wasn't a fan, but it was a huge hindrance at the beginning. I had to plow through a large portion of book before I was all caught up on what was happening. A little synopsis of book 2 would have been greatly appreciated. 
 Anyway, once I was back on track with the plot, it moved along quite nicely. I appreciated the shift between Lena and Hana's POV. I thought they had distinctive personalities and were written accordingly. Jumping back and forth allowed for tons of excitement, without all that boring filler. The writing itself was stronger than I remember, with some fantastic descriptions and metaphors. 
 The ending? I can imagine there will be some people who are bothered by the end, because it's not all happy, and filled to bursting with the love that the characters have been fighting for. I don't think that "happily ever after" would have fit with the books though. It's not a happy series. It's bitter and sad at times, so I think the ending fit well. Not disappointed at all.