It's based on the series of books "The Dresden Files" by jimbutcher. They are actually quite good.

As an added bonus, James Marsters does the narration for the audio books. (Squee!) In fact, there was a lot of talk at first about him starring in the series himself. But, in the end, he didn't want to move to Toronto - which is where it is being filmed. (Though, as I said, the actor they cast does quite a good job of sounding exactly like him!)

I'm looking forward to it; it looks like it will be really good.