Anna Series by Kendare Blake

Cas Lowood has inherited an unusual vocation: He kills the dead. So did his father before him, until he was gruesomely murdered 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. They follow legends and local lore, destroy the murderous dead, and keep pesky things like the future and friends at bay... moreCas Lowood has inherited an unusual vocation: He kills the dead. So did his father before him, until he was gruesomely murdered 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. They follow legends and local lore, destroy the murderous dead, and keep pesky things like the future and friends at bay. Searching for a ghost the locals call Anna Dressed in Blood, Cas expects the usual: track, 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, now stained red and dripping with 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. Yet she spares Cas's life. less

It's been months since the ghost of Anna Korlov opened a door to Hell in her basement and disappeared into it, but ghost-hunter Cas Lowood can't move on. His friends remind him that Anna sacrificed herself so that Cas could live—not walk around half dead. He knows they're right, but in Cas's eyes, no living girl he meets can compare to the dead girl he fell in love with. Now he's seeing Anna everywhere: sometimes when he's asleep and sometimes in waking nightmares... moreIt's been months since the ghost of Anna Korlov opened a door to Hell in her basement and disappeared into it, but ghost-hunter Cas Lowood can't move on. His friends remind him that Anna sacrificed herself so that Cas could live—not walk around half dead. He knows they're right, but in Cas's eyes, no living girl he meets can compare to the dead girl he fell in love with. Now he's seeing Anna everywhere: sometimes when he's asleep and sometimes in waking nightmares. But something is very wrong...these aren't just daydreams. Anna seems tortured, torn apart in new and ever more gruesome ways every time she appears. Cas doesn't know what happened to Anna when she disappeared into Hell, but he knows she doesn't deserve whatever is happening to her now. Anna saved Cas more than once, and it's time for him to return the favor. less