Anna Dressed in Blood

Anna Dressed in Blood, was the first of a series written by Kendare Blake. It is written about a ghost hunter named Theseus Cassio Lowood and his adventure to find and kill one of the strongest ghosts he's gone up against in his life; Anna Dressed in Blood.

WARNING: Spoilers may follow!

Blurb
Just your average boy-meets-girl, girl-kills-people story... Cas Lowood has inherited an unusual vocation: He kills the dead.

So did his father before him, until his gruesome murder by a ghost he sought to kill. Now, armed with his father's mysterious and deadly athame, Cas travels the country with his kitchen-witch mother and their spirit-sniffing cat. Together they follow legends and local lore, trying to keep up with the murderous dead—keeping pesky things at bay.

When they arrive in a new town in search of a ghost the locals call Anna Dressed in Blood, Cas doesn't expect anything outside of the ordinary: move, hunt, kill. What he finds instead is a girl entangled in curses and rage, a ghost like he's never faced before. She still wears the dress she wore on the day of her brutal murder in 1958: once white, but now stained red and dripping blood. Since her death, Anna has killed any and every person who has dared to step into the deserted Victorian she used to call home.

And she, for whatever reason, spares his life.