This is a wonderful prequel to the Dresden Files. It's not often that authors of novels get to write the comic books based on their books (although it seems to be happening a little more frequently now with Marvel's adaptations of King, Hamilton and Card books that the authors at least have a hand in), so I was glad to see Butcher not only approved of the prequel but wrote it himself.
Because it's a prequel, the only on-going characters we get to see in action are Harry, Bob the Skull, and Lt. Karrin Murphy of Special Investigations. There's a cameo by Murph's second-in-command Ron Carmichael and a panel or two that show Elaine and Justin and hint at some of the bad stuff Harry encountered as a teen.
Ardian Syaf's artwork is not the greatest panel work I've ever seen, but there are some great moments. His Harry is appropriately tall and gangly, and he draws animals incredibly well (important, since the story takes place at Lincoln Park Zoo). I'm not particularly impressed with his interpretation of Karrin Murphy, or of the look of Harry's blasting rod (which is made to look like a run of the mill stage magician's trick wand).
It's a good strong story though, recommended if you're reading the Dresden books.