Storm Front : The Dresden Files, Book One, 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's business as a private investigator has been quiet lately - so when the police bring him in to consult on a grisly double murder committed with black magic, he's seeing dollar signs. But where there's black magic, there's a black mage behind it. And now that mage knows Harry's name.

Magic - it can get a guy killed.