Death Masks (The Dresden Files, #5) by Jim Butcher

Meet Harry Dresden, Chicago's first (and only) Wizard P.I. Turns out the 'everyday' world is full of strange and magical things - and most of them don't play well with humans. That's where Harry comes in. Harry Dresden should be happy that business is good - makes a change. But now he's getting more than he bargained for: a duel with the Red Court of Vampires' champion, who must kill Harry to end the war between vampires and wizards; professional hit men using Harry for target practice; the missing Shroud of Turin (less missing than expected) and a headless corpse the Chicago police need identifying ...Not to mention the return of Harry's ex-girlfriend Susan, still struggling with her semi-vampiric nature. And who seems to have a new man. Some days, it just doesn't pay to get out of bed. No matter how much you're charging. Magic - it can get a guy killed.