The Devil You Know (a Felix Castor novel)
The Devil You Know is an urban fantasy. Wikipedia describes urban fantasy as a subset of contemporary fantasy meaning that the supernatural exists and is accepted in a world not unlike our own. If it is in a city then it is urban fantasy. You could also classify it as a supernatural thriller. In any case, it would be safe to put Carey's Felix Castor in the company of Jim Butcher's Harry Dresden and Kim Harrison's Rachel Morgan.
Carey might be better known for his writing in comics where you will find his name on titles in the DC Comics Vertigo imprint such as Hellblazer and Lucifer as well as Marvel comics like X-Men and Fantastic Four.
The Devil You Know is the first in the Felix Castor series. It is set in London in a world where the dead began "...to rise is sufficient numbers that it wasn't an option anymore just to ignore them." In addition to ghosts, there are demons and loup-garou (were creatures, sort of). Felix is a freelance exorcist who uses a tin whistle to draw the ghosts to him then cause them to move on. Where they move on to isn't discussed but Carey sets it up to be explored in later books in the series.
Felix needs money to pay his rent and takes a job to exorcise a ghost from an archive in spite of a warning from a demon who is also possessing a friend of his. What should be a straightforward exorcism gets complicated as Felix tries to find out what is anchoring the ghost to the archives. The story takes on more twists when a gangster who lures young women from Eastern Europe into sexual slavery gets involved and someone sics a succubus onto Felix.
The story seems a bit drawn out and overly long at times but Carey is creating a convincing world and uses the detail to describe the rules of this world. Consider his take on loup-garou. We are used to reading about were creatures as humans who take on animal form. In Felix's world, ghosts take possession of a animal and shape it into something resembling a human. I appreciate that Carey is able to add fresh elements to a genre with a lot of competition.
The Devil You Know concludes with Felix taking on (unwillingly) an unusual partner and setting the scene for an interesting sequel. Speaking of which, the other books in this series are
Vicious Circle (2006)
Dead Men's Books (2007)
Thicker that Water (2008)
You might have to wait a bit as they are first published in the U.K. and not immediately available in the U.S. Amazon doesn't show a listing for Vicious Circle.