Bloodlands is the first book in the Mariah Lyander series by Christine Cody (Chris Marie Green) from ACE.
It was called the New Badlands, home to the survivors of a cataclysm that altered the entire nation. Then the vampires arrived, and it was rechristened the Bloodlands.
Not because of the vampire, but because of the gun-for-hire who'd decided to slay every monster in the country by any and every means necessary.
Sounds good. :)