If you like vampire stories because they show vampires in a sympathetic light, make them lovable, understandable, marriageable or sparkly, this is not your book.
If on the other hand, you appreciate the more subtle attractions of a race of beings that never die on their own, are obsessed with eating their favorite food all day night, are only interested in their pre-vampire friends is as an entree or as a new recruit, and who repeatedly draw the negative attention of hunters who have a visceral dislike of the vampire lifestyle, then you will truly appreciate 13 Bullets.
I read this book after completing the Twilight series (which I also liked), and the contrast between Stephanie Meyer's and David Wellington's idea of vampires is pretty stark. In David Wellington's universe, there are no "vegetarian" vampires, they all need human blood, and lots of it. His vampires are pale, but they aren't beautiful (think Nosferatu on steroids). You wouldn't want to kiss one because of all the extra teeth they develop and the fact that they usually are biting you with said teeth. They're indestructible, super strong, fast healing, bald as cue balls, have funny looking ears, and unruly dispositions. They live forever, just like the Cullen family, but one of the wrinkles about being a Wellingtonian vampire is that as you get older, you need more blood, so that by the time you are a hundred years old you're never going to get enough of your favorite drink with out making some more vampires to help you satisfy your appetite by collecting blood for you. It's sort of an undead pyramid scheme, except that no one who is recruited gets to leave the Amway clan once they join.
And how do you get recruited? Well, you don't get bitten. Instead, you get psychically invaded by the vampire, who leaves a portion of his evil soul in your mind, that then tries to convince you to "accept the Curse" of the undead by killing yourself. This vampiric Trojan horse never goes away, even if you manage to kill your attacker. So, have a bad day at work or start feeling a little down on your life, and you're starting down the slippery slope to an all liquid diet.
So if the vampires are the bad guys, who are the good guys? Like Twilight, this book has a heroine who is the focus of the book. However, she is almost entirely unlike Bella Swan in every way. Laura Caxton is a grown up whose parents are dead, as a result of sad but mundane causes. She is a Pennsylvania state trooper, and is a lesbian in a committed relationship. She is driven to succeed in her life, but unsure of herself because she doesn't realize her worth and her inner strength. She is also, for reasons she doesn't understand, a vampire magnet. As a person with real strengths and flaws, she is a sympathetic character, and one that the reader hopes will persevere, and survive until the next book (at least).
Her boss is less sympathetic, but just as flawed. Jameson Arkeley is a Special Deputy in the US Marshals Service who has dedicated his career to rooting out and destroying the vampire menace. He's grouchy, uncompromising, esoteric, and rude. He doesn't tell Caxton his complete plan, until it's nearly too late. He serves as the Van Helsing of this dark tale, providing the backstory, and describing the ways of Wellington's vampires. He is also knowingly and unknowingly enmeshing Trooper Caxton in his crazed quest to destroy evil.
The story is set against the backdrop of rural Pennsylvania, and anyone who has lived there will instantly understand the author's characterizations of the peculiarities of that state, especially the backwater areas where the stranger people Pennsylvanians dwell.
This was a good story, so I won't wreck it for you by sharing much of the plot. Just watch out for the unexpected plot twist at the end that brings everything into a much sharper focus. I'm looking forward to the next book, which is going to give a new twist to the bizarre history of Gettysburg, PA.
By the way, the fundamental difference between Twilight and 13 Bullets is that the former is a love story with vampires in it, while the latter is a vampire story, period.