Kendare Blake's Anna series (although there are only two books so far, so it may remain a duology, I'm not sure).
Theseus Cassio (Cas for short) is not a typical teenage boy, by any definition of the word "typical." He has taken over the family business - dispatching murderous ghosts from off this earthly plane. This work has the family move frequently from place to place, all over the world, wherever the latest legitimate tip sends them; this time, they've followed a tip to Thunder Bay, Ontario, where Cas intends to find and "kill" the ghost known as Anna Dressed in Blood, a teenage girl who was found murdered in the 1950s, and whose ghost has been busy literally ripping apart anyone unfortunate enough to set foot in her house since.
For Cas, this case feels different from the start, and his instinct proves true when Anna turns out to be unlike any ghost he's yet encountered. Will he be able to finish the job he came here to do?
I got this book back when it was new and making its initial rounds in the book blog community, but I only just got around to reading it; the premise and the cover art really drew me in. I enjoy paranormal fiction and ghosts, so this seemed right up my alley. For the most part, it didn't totally disappoint.