Dresden Files 3: Grave Peril - Jim Butcher

The third case file from Harry Dresden, a modern-day wizard who gets into some seriously challenging situations. 

Harry has faced some terrifying foes during his career. Giant scorpions. Oversexed vampires.  Psychotic werewolves. It comes with the territory when you're the only wizard in town. But in all Harry's years of supernatural sleuthing, he's never faced anything like this: the spirit world's gone loco.

All over town, ghosts are causing trouble - and not the door-slamming, boo-shouting variety. These ghosts are tormented, violent, and deadly. Someone is stirring them up to wreak havoc.

But why? And why do so many of the victims have ties to Harry? If Harry doesn't figure it out soon, he might just wind up a ghost himself. Magic - it can get a guy killed.