I sort of liked this novel, and no doubt many people loved it. Symon Bryson is Harry Dresden/Harry Potter character in a Dan Brownish world. The plot moves along with lots of action. Supporting characters are distinguishable from one another. The writing is clear, and edited. There are zombies and demons, with some gore but not overly done. Many people will enjoy this story, and I'm confident that R.B. Wood will develop the characters and world further in future novels, much like Jim Butcher fans claim about his work.
For me, the novel never really clicked. Best I can tell is that I grew annoyed with some of the overly done things. As an example, Symon tells us he is a wise ass, then he says wise ass things, then other characters call him a wise ass. Over and over, throughout the novel. I grew tired of hearing it. Some of the Symon's dialogue was funny, much was strained - but then I know some wise asses and they often try too hard. The other annoying factor was Symon's regurgitation - so many references or actual accomplishments that I could predict it. Little things like that, mostly nits, I know, but the connection between a reader and a novel can hinge on small things.
If I had to put a finger on a larger issue, I'd I had the feeling that this novel was riding on coattails, which is okay if the author inserts something special. Mixing the Vatican, the US Government, and a group of wizards could be fresh, but, for me, the story never fleshed out. Perhaps there's too much of the typical formula: a young man (Symon) with flaws is the chosen 'one' who, despite the clear and greater talents of those around him, still, much to his surprise, HE is the only one who can save the day. The reader needs to understand why he is The ONE at the end, and Symon having a lot of passion in his heart seemed like a weak point.
So, I had issues, but then I over analyze things. As a YA novel, it works just fine.