Grave Peril (Dresden Files Book 3) by Jim Butcher
A fun plot introducing a new friend for Dresden: Michael, one of the ultra-holy Knights Of the Cross. There are three such Knights who work tirelessly behind the scenes for the good of humanity.
At the same time, Michael holds down a mundane job. He has several kids and a wife who worries about him (much as a copís wife would), and who disapproves of Dresden as an obvious bad influence upon her husbandís life expectancy.
Dresden (while feeling very guilty every time Michaelís wife glares at him) teams up with Michael to solve a new mystery. An evil sorcerer is stirring up ghosts and torturing them into wreaking havoc on the living world.