Number three in the Dresden Files series by Jim Butcher...
A new character is introduced in this one that I really liked. Both the character himself and what he brings into the whole Dresden universe. The guy is basically a Knight Templar, with the sword and the chain mail and the white robe (I know it has a name that isn't "robe" but I can't come up with it). He has an incredibly strong faith and that along with the sword is what he uses to fight the nasties with Dresden.
It very much reminds me of the way Tanya Huff's Blood Books treat religion. Acknowledging that there are bad supernatural forces, but there's good ones too. I love that! It makes the universe so much more interesting to me. It's not just the humans against all the bad stuff, there's good out there too.
Plot-wise there's something torturing various ghosts in order to weaken the barrier between their world and ours which would allow all kinds of nastiness to get through, including something that Dresden and Michael (the knight) thought they had dealt with already. This, of course, would be a Bad Thing. We also meet Dresden's godmother who is an interesting... person. I'm looking forward to learning the whole story behind her and how they're connected.