Never has a free book captivated me as this one. I am very impressed with the flow of the work - very fast-passed, but never rushed (except where the author wanted you to feel that). I also appreciated that, while I am from another country and occupation, I had no trouble understanding any of the jargon used. Crowson worked things in such a way that any lay person could understand the technicalities of the police work and occasional local slang/accents.
I would have liked more fleshing-out of the characters a bit more...a bit more background to help me understand the different relationship dynamics in the work (but this is just my quirk and does not take away from the story at all).
Finally, I have to tip my hat to the absolute brilliant notion of offering this free. There are more than one of us hooked and the author will be making sales from now on. Good marketing!