Storm Front (The Dresden Files, #1) 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 is the best at what he does - and not just because he's the only one who does it. So when the Chicago P.D. has a case that transcends mortal capabilities, they look to him for answers. There's just one problem. Business, to put it mildly, stinks. So when the police bring him in to consult on a grisly double murder committed with black magic, Harry'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. And that's when things start to get . . . interesting. Magic - it can get a guy killed.