I got this for the Butcher short story, since I've finished the novels published so far and am now working through all the shorts/graphic novels that I can find. I thought this format worked well for the Dresden stories, since Butcher has a tendency to repeat himself in the novels (we know about Mister, Bob, the layout of the apartment already!) but was space limited to minimal fluff. This fit in between the last two novels currently out (Turn Coat and Changes) and filled in (spoiler alert) what happened to Michael after Turn Coat. I finished Changes wondering why he never got around to talking about Michael, and this explains why. Also explains something that Uriel says in Changes.
I started the Kat Richardson story as well, but it seemed, much like the Butcher, that it was in between novels and I felt like I needed more information, it didn't stand alone. I assumed the same would be the case for the other two and didn't bother.