The Dresden Files

If you haven't read the Dresden Files and are looking for a different take on the detective genre, you should give this show a shot.
On the other hand, if you're looking for a TV version of Butcher's books, you're going to have to wait until somebody tries again, because this isn't it.
The books are urban fantasies about a wizard, Harry Dresden, who makes his living as a PI. The TV show is a detective drama about a PI who also happens to be a wizard. This might sound like a subtle distinction, but if you've read the books and watched the series, you'll know otherwise. The books are full of magical creatures, demons, spells, and everything you'd expect from a fantasy, all while Harry solves his cases. The show is mostly about police work; in fact, if you subtracted out the fantasy elements you'd have a workable, if dull, detective show. Try that with one of the books and the whole thing falls apart.
Most of the differences between the two versions can be chalked up the needs of catering to a television audience versus the author being able to write pretty much whatever he wants. This is all well and good... except that there are so many differences that they sometimes render the TV version unrecognizable as being based on the books.
Lots of people want to know why this show didn't do better. I can think of two. First, unless a show is a runaway success, a rarity on most stations but especially on SyFy, getting renewed is difficult at best. Two, from personal experience the show failed to capture and hold the interest of a large percentage of its target audience: the fans of Butcher's Dresden Files.
Sure, a show can theoretically survive both of those things, even together. But if large portions of the audience they made the show for aren't watching, it wouldn't have taken much for the network execs to look for something new.