Aiden is the love interest and a pure blood. He is the one who saves Alex and takes her back to the Covenant. He also agrees to train her and get her up to speed with her peers. He also develops feelings for her. Which is forbidden as pure bloods are not to dilute their blood.
Seth... oh Seth. He is hilarious and also the Apollyon. He comes into the story maybe midway through and helps Alex discover very important things about herself. He is also very sarcastic and full of himself. Who wouldn't be with his kind of power though?!
The story is actually pretty predictable. It turns out her mother isn't dead and that she has been turned into a daimon and is going to come after Alex. Also it's pretty damn obvious how she will be the second Apollyon with how she is reading about them in the textbook some chapters before. Even though I saw everything coming, it's still amazing! I enjoyed every single page and found myself never wanting to put it down.
There has been a lot of comparisons between Vampire Academy and Half-Blood. I loved both books. I can see huge similarities between them. They both have a strong 'half' female lead, forbidden love from a guy who trains her, a reason for leaving the school before the start of the book, and an almost sex scene. Yes, I'm sure there are even more but honestly, what does it matter? I honestly prefer this book to Vampire Academy. It's so great. If you haven't read this series yet, grab a copy and get ready to be sucked into an amazing world.