Hmmm... I don't really know how to write a proper review for this book (or to justify my action in giving this 2-stars, which means a no-no in my dictionary). The premise is actually very interesting: 
 "Demons who live among human" 
 How many YA-fantasy book that are actually dealing with demons? I don't know about you, but I rarely see one. And when I know that the "demons" here are different than your-average-demons, I squealed in excitement! 
 But, it sadly didn't last for long. 
 IT WAS BORING.... 
 The premise is great, there are lots of conflicts and interesting characters, but it is EMOTIONLESS.... 
 I finished the book with this blank expression on my face from beginning till the end. 
 You see, sometimes author focuses more on the conflicts until, they forget to define the characters with emotions, human emotions And this maybe one of my problems with this book. The character were defined by their conflicts, not characteristics/emotions. I could tell you about how Dee struggle with abusive/alcoholic father, and how broken she is because of it. BUT, I don't feel it. I know it, but I couldn't sympathize. She keeps saying that "she's broken and beyond repair." But she never shows it. 
 I think the saying of "Show, don't tell..." should be applied heavily to this book. 
 Not only that, I feel the reactions from the characters are sometimes off... They don't feel human... Is it because they've sold their heart? *pun intended* One thing I know for sure is that it's the fault of the author, not because of them being 'heart'less. 
 The most interesting character in this book is the Daemon/demon, but sadly the author decided to never thoroughly explore him or his community. There are a few glimpses or historical evidences that provide background for the Daemon/demon, but it somehow feels like a 'teaser'. As if there will be a second book that would dig deeper about the origin of the demons. 
 All in all, it was a book with great premise that sadly failed in execution. 
 P.S. Don't you dare to pull THAT ending. I hate this more, for that cheap-unnecessary-rushed drama just to create a 'huge' impact in the ending. bzzzztt...