I've read all of Rachel Vincent's Unbound series and her Shifters series, so I'm pretty familiar with her style. I'm not sure what to make of this one. 
 On one hand, I liked the characterizations, world building, and post-demon apocalypse history. On the other hand, while there wasn't much romance, I honestly thought this book could have done without it at all. It has so many other things going on that the author could have explored, I just felt like she had to put in a romance because it's a YA requirement or something. It was a very weak point and while there wasn't much of it, there was a lot of instalove/"really like" from Finn to Nina just because she's gorgeous. The plot is fast paced and I finished the whole book almost in one sitting, so I suppose the author didn't have time to touch on a few things that I think could have been more in depth. But I'll just point out two things: 
 (view spoiler)[Vincent could have spent a little bit more time addressing the ethics of Finn jumping around in other people's body without their permission and running around doing things in their body. At one point in the book, he jumps into the body of a former lover of Nina's and kisses her, she narrates something along the lines of him putting the body/mouth of her former lover to better use. Ok, here's the quote: "Then Finn kissed me, and I was pleased to discover that he made much better use of Jacob Gilbert's mouth than the original owner probably ever would." I don't know about anyone else, but that really took away any romantic aspect of the kissing for me and kind of squicked me out. Sure, the victim/host doesn't remember it, but it wasn't done with permission either. Nina does struggle with Finn's lack of physical body for a bit but also seems to get over the fact that he takes over OTHER people's bodies pretty fast. As a huge Supernatural fan (and Castiel the angel fan), I think Vincent should take a little longer to explore the issues behind taking over someone else's body and possibly getting them killed/hurt/etc.. I mean, like I said, she probably sacrificed this for plot and action, but that kissing scene was pretty cringeworthy. 
 At another point in the book, Finn takes over someone else just in order to push them in front of Nina and to take bullets for her. This is also glossed over quite a bit. Look, if his special power/ability weren't to take control of people from inside, what he essentially did was shove someone else in front of several bullets to save the person he likes. That's incredibly messed up but my issue isn't that Vincent wrote the scene, it's that Nina doesn't react to it other than "Finn had thrown an innocent man's body between me and certain death." And then...that's it. It's never mentioned again. This book is very comic book superhero in the sense that if you're one of the main characters, great, if not, you're just going to be one of the nameless, faceless masses of "innocents" that are collateral damage and no one really cares anyway - akin to all the background people who die in Avengers 2 but we're really only emotionally invested in the lives of like, Quiksilver and the few handfuls of people he's saving. Or the entire city of Gotham being threatened, but let's throw in a few symbolic schoolbuses of children needing to be saved. 
 It's not problematic, per say, but it's like Vincent raised the stakes so much that it got a little too ridiculous. To me, dozens of people here and there getting killed as collateral damage doesn't really reinforce the evilness of the Church or demons more than a few well placed examples, but if you're going to write in the deaths, make it contribute something to the story. 
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