In the hundreds of books I've read, YA and otherwise, there have only been a handful that I just didn't finish. I don't mean books that I didn't start - if I don't get at least 10% into it, I assume that the book is just not for me, which is perfectly fine. However, I struggled with this book and actually got about halfway done with it, admittedly by skimming over several utterly superfluous sections, and finally concluded that at that point, even the best ending wouldn't change my mind about the book. 
 The idea is interesting, if not exactly new. A demon attending Catholic church school, haha. The main problem was just that Jael was so utterly unlikeable and, dare I say it bluntly, stupid. Yes, I get that as a teenage protagonist, she will have rebellious aspects and make mistakes. However, I don't care exactly how controlling and strict her father is, Jael's actions and personality are just not even believable. 
 One aspect of YA fiction that I generally like is the bildungsroman themes that are natural to any story with teenage protagonists. To differing extents, we all go through that period of life where we think the whole world revolves around us. This lack of perspective is generally one of the things that drives character development and maturity in YA fiction - the increase of responsibilities and the seriousness of the consequences for failure cause the young girl or boy to increasingly realize that the world isn't easily divided into black and white. 
 Unfortunately, Jael never even got close to that point. Since I didn't finish the book, it's possible that something happened in the later half that showed some kind of change to her bratty character, but given that I did read half the book, that's too long of a delay in any case. 
 One side thing that I will note: the typeset for the book and chapter titles is indeed pretty nice.