I'm a little bit torn on this one. I liked the story, for the most part, and the characters, but there were several things that bothered me. 
 The racial metaphor of the Darklings is a little bit too obvious, I think. Some things seemed to happen a bit too quickly, others a little too easily. There was a brief love triangle that felt kind of forced, but it certainly had a different approach to the triangle that was interesting, and thankfully it didn't last long. Sometimes the characters' change-of-hearts seemed rather inexplicable and too quick. 
 The only other thing that really annoyed me was the use of "Fragg" as a replacement curse word for "f**k". When books use other terms as swears, it doesn't bother me if it is a term with context to the book's world. For example, this book uses "nippers" as a derogatory term for the Darklings. As they are vampires who bite people, this makes sense, even if it adds to the heavy-handedness of the racial metaphor(nipper sounds a lot like a terrible, racist term in our society, after all). Similarly, see the word "mudblood" or any of the "Merlin's beard!" type oaths in the Harry Potter series: the former is explained to the audience, the latter makes sense in a magical world. However, the word "fragg" is never given any context except as an obvious replacement for "f**k". This makes it pretty obvious that it is only there to avoid the f-word, rather than as a legitimate piece of world-building. If you can't come up with a decent contextual reason for that word to exist, just use the swearword. Honestly. It's YA, sure, but the characters are in their teens. Trust me, they are familiar with the word. 
 Having said all that, I did like the world in general, and enjoyed the main plot. I'm just not sure I enjoyed it enough to continue with the series. It's a debut novel, so there's certainly potential for improvement(and lots of room for it) So, I'm giving it 3 stars, but maybe it's more like 2 and a half.