Haunted
by Kelley Armstrong

Eve Levine made a bargain with Fate, and now she's come to collect, sending Eve off on a quest to retrieve the soul of an escaped demi-demon. Playing ghost world bounty hunter isn't exactly what Eve had in mind for an afterlife career, but a deal is a deal. Eve never breaks a promise...even when the cost of repaying that debt turns out to be more than this ghost can afford.

This is part of a wonderful series of books. You can jump books - they are written so you can pick it up anywhere and not be totally confused. Although the narrator changes, the books take place in chronological order, in the same universe with the same cast of characters. A narrator from one book will appear as a character in another. Events from one book will be referenced in others. Some subplots carry on from novel to novel, bridging narrators. It's done very cleverly and there are always characters that you build a relationship with. Another series that I have to order from my local Dymocks. There are also quite a few shorter stories dealing with teh same characters on the web.

http://www.kelleyarmstrong.com