Hate Machine — Stephen Blackmoore

The eighth book of this dark urban fantasy series follows necromancer Eric Carter through a world of vengeful gods and goddesses, mysterious murders, and restless ghosts.

If there's one thing Eric Carter can count on, it's his past coming back to bite him in the ass.
 
Gabriela Cortez, La Bruja, has had her soul trapped... somewhere, and the only one who knows how to get it back is the Oracle of Las Vegas, a powerful artifact that Carter helped create almost thirty years before. It doesn't just predict the future -- it makes things happen, influencing events to reach the goal it wants.
 
Only somebody's gone and stolen it, attempting to turn it into an artifact that doesn't just change the future, but also the past.
 
Eric needs to find it and steal it back before this comes to pass. If he doesn't, Gabriela's soul is lost. And quite possibly the future as well.