Apollyon starts out with Aiden trying his hardest to bring Alex back to herself. She's been taken over by the connect to Seth since she Awakened. She's said and done some really horrible things, but Aiden isn't going to give up. I seriously love Aiden. He was so awesome with Alex. He never gave up on her.
And once she comes back to herself they must go to the Underworld to figure out a way to stop Seth. The things Alex learns makes her feel like there is a huge chance a lot of them won't make it once everything is all said and done. And she's right on one aspect, they do end up losing another friend.
This book has so much in it. It show's more about Alex and Aiden's relationship. It also shows Alex getting to know more about her father, and getting closer to her uncle. And in the end, Alex does something so extremely brave that she is given the chance to see someone who she had once lost.
I can not wait for the next book. This series is really really good, and I love reading it. Now I just hate waiting for the next one :)