Proven Guilty (The Dresden Files, #8) 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 has no friends on the White Council of Wizards, who find him brash and undisciplined (and they may have a point). However, now vampire wars have thinned out the wizards a little, they need him. So before he can blink, he's assigned to investigate rumours of black magic. Harry's other problem is an old friend's daughter - all grown-up and in trouble already. Her boyfriend insists he's innocent of something resembling a crime straight out of a horror film. This first impression turns out to be ...well, pretty accurate, as Harry discovers malevolent entities feeding on fear. All in a day's work for a wizard, his dog, and a talking skull named Bob. Magic - it can get a guy killed.