[I received a copy through NetGalley, in exchange for an honest review.]
3.5 stars. Entertaining and somewhat funny at times, while still conveying a sense of danger—alright, maybe not terribly frightening per se for me, as I don't frighten easily when reading books, but I think it has the right potential nonetheless. Half the Host at least was creepy in more ways than one, from the Shepherd with his glasses to the Prisoner with his shears... and even the Innocent, for the questions he raised (who would leash a *baby* as their pet ghost, really?!). The Host wasn't a bunch of good guys, apart from a couple, and even those remained on the fence and never said the whole truth, only intervening at a "right" moment that could've been just a tad bit sooner for good measure.
As I'm a sucker for necromancy in general, of course I couldn't help but look for the questions it raised. And there were several. The baby I mentioned, for starters. Why Luke's father turned to such a type of magic, and why he bound such a large Host, when nothing at first indicated he even needed one (this is explained later in the book). Whether Luke would accept this part of his inheritance and be lured towards a desire for power, or try to remain who he was and have a normal life. Choices to make, and forgiveness. This wasn't just about getting rid of a bunch of ghosts, but also choosing to protect or to condemn other people.
I liked the dynamics between Luke and Elza—there's a smidge of a budding romance in there, one that doesn't detract from the plot, and develops slowly: good! Luke realised he couldn't clutch forever to his little life as one of the "popular" crowd, in the face of something much biger and dangerous. Elza was resourceful, and overall a nice person, trying to help people who had been treating her like an outcast just because she didn't want to fit their mould. Holiday, too, was a bit of an ambiguous person: picking her friends among the popular ones and discarding the others, but not to the extent of becoming a mean girl. She was barely more than a crush, yet at least she was a believable one. As for the lawyer, well... Even though you don't get to see him much, he was perfectly cast in his role.
Oh, and Ham. Ham the deerhound. A very short part of the novel is actually from his point of view, and that was quite funny. It would've been annoying if it had been longer; kept to a few paragraphs, it wasn't, and definitely made me smile.
Other characters were less defined, unfortunately: Mark, Kirk, even Luke's mother, who remains ill/asleep for most of the novel. That last one was a bit of a letdown, as in turn, it was difficult to properly get to know her and to share Luke's worries for her for any other reason than "she's his mom".
Sometimes Luke's reactions made me cringe, as he seemed to switch from one to the other real quick. It didn't happen that often, and it could be explained by panic and worry; only it made me wonder why he'd get such reactions. (For instance, when it's been made clear that you're haunted by ghosts and that those have put a certain person in a coma, dragging that person to a hospital won't be very useful, especially not considering all the people who die in a hospital.) A couple of times, too, I picked some absolutely obvious clues that totally eluded the characters (re: the familiar); on the other hand, all things considered, maybe that's a case of being too genre-savvy on my part, so I can't very well hold it against characters who were either totally new to the supernatural, or barely fledglings (Elza admitted herself she was self-taught).
There was a slight lull in the middle while the characters were powerless and trying to figure out what to do—not that Luke's father had been very helpful to begin with. They came up with an interesting idea in the end, so I forgave them.
The writing was OK, nothing exceptional, nothing blatantly annoying either. It should flow nicely enough for the intended audience. (Also, my Kindle copy was a bit oddly formatted; however, this is an ARC, so likely to change.)
Conclusion: 3.5 stars, because in spite of the points I mentioned, I pretty much enjoyed it. The story is also self-contained, yet open-ended enough to leave room for a sequel (someone's bound to come back and collect their dues here, not to mention what may or may not happen between Luke and Elza, and how their fellow pupils would react to it).