I want to be bias and tell you this is this is the best thing in the world. I can't. It's a great book with many flaws.
I still think you should read it.
The first problem is that the story and it's advertising treat this as a super hero story. It's not. This is much more like Hellboy's BRPD meets the movie Push. So let's get that straight. No capes and crusaders. A teleporting demon, a sentient zombie, a mage, a time traveler, a millennium old demon hunter, a serial killer, an insane android? Dark demons and mythological gods? A fight against ancient Lovecraftian forces from beyond our world?
The biggest strength of the series is that the ideas presented are novel and unique. The concept of the undead is new and fresh. The main character's abilities are very distinctly unique. The constant plot twist revelations are fresh and intriguing, and planned from page one. You can tell a lot of thinking went into the world, the characters, and how everything works together.
That said, the actual writing is a mixed bag. At times the dialogue and narrative works. Really works really well. At other times the dialogue is stilted, shallow, and (especially in the third book) prone to pointless pop culture references. What makes it all work is a set of interesting concepts. The trilogy ends wrapping up several ends conveniently and then dangling a dozen more unfinished storylines. This I find in it's favor, as it's geared to lead into a second trilogy. It's flaws are entirely attributed to amateur narrative. Forristal has great ideas but this is his first published material done in his spare time, so the writing itself is not as polished as I'd like. As long as he keeps at it, I am certain he'll find his unique voice.
At the end of the day I would say read it. It's a fun read and I never had to force myself through it. The ideas are fresh and fun. I look foreword to his sophomore effort and think that once he's polished his narrative this series will be amazing.