Thicker Than Blood

Dave Carver doesn't wear shining armor or ride a white horse, but he does carry a sword. For centuries, the Knights of the Round Table have defended humanity from the worst monsters that exist beyond the realm of reason. Dave is a Knight of the Round Table. Or he was.
After a traumatic stay in a vampire prison camp, Dave has retired from his life of monster hunting and living in a dingy apartment in Manhattan, but when he's attacked by an agent of the vampires he must pick up his sword to defend New York City.
Dave is going to have to contend with a double-dealing diplomat, a pair of duplicitous vampire siblings, and a traitor within the Round Table on his quest to stop the vampires from turning the human race into a glorified cattle ranch.
And if he fails, the world is going to get a whole lot bloodier.

Thicker Than Blood is the first novel in the Dave Carver series.