Honestly, with the tagline "There are only thirteen bullets between the world you know and the world they rule", and the dramatic final fight scene, I am getting the impression that this was an expanded short story.
The idea of how vampirism is transmitted is new and really damn smart. Once you're infected by vampirism in potentia
--which depending on the power of the vampire can be done in a variety of ways; the particularly old or strong ones can apparently do it at will by making eye contact--then you become a vampire *if you kill yourself.* And the vampire having its hooks in your brain may hurry this process along; they can inflict horrible dream sequences which start to make suicide and vampirism seem very appealing. Ties into the old suicide legends; maintains the concept of infection; gets rid of the "doesn't everyone a vampire kills become a vampire" thing, which incidentally is probably a useful thing as the vampire in question are really horribly brutal.
(The book runs with an alternate history--one in which vampires have always been known to exist, but were beaten back. They're currently thought to be extinct in the wild--the book suggests a setting where one pops up somewhere in the world perhaps once every decade or two.)
There are also half-deads--zombie bodies, coherent minds--that have been fed vampire blood and are loyal to the vampire, right up until they fall apart. (There's an implication that vampires don't have to create half-deads out of the living; at one point Scapegrace quickens (awakens, enlivens) a newborn's skull and hands it to someone, simply so he doesn't have to watch them closely--if they don't cradle it in both hands, it will start screaming. However, that might've been something rather slightly different. I don't mind not getting a catalog power listing.)
However. The book presents vampires as being tougher in direct proportion to how much blood they've drunk--I believe the phrase "so full of blood a bazooka couldn't hurt him" is applied to a vampire who's gorged on four or five people at one point. Similarly, the climactic fight scene involves a vampire who's fed so well that she's completely ignoring bullets fired at her heart from point-blank range. And yet this vampire is defeated by being tripped through a window (okay) which then shatters and cuts her to pieces (what?
), causing her to lose so much blood that our protagonist can stab her through the heart several times with a jagged metal rod, killing her.
Given how hard that fight was played up, I felt rather cheated.
 Have I mentioned how much I love this name? It's not Gabriel Grey, but it's damn good.