Interesting read.
While it is a theoretical and analytic paper, it does present some good arguments. It also does say that the introduction of conceal carry laws did nothing for the rates either.
What I find interesting is his analysis of things he believes did decrease homicide rates, namely the increase in police force during that time, the decline of crack use, the increase in prison population, and the legalization of abortion, the last two being the most significant contributors.
His supporting argument for why the Brady Hand gun law had zero effect on homicide rates was the existence of the black market. While I won't argue that many denied a gun through a normal dealer didn't pursue a gun in other fashions, it's dishonest to claim that all would have (In reference to his belief that the Brady law had ZERO effect). His analysis of the data also takes into account the overall decline in homicide rates, but he doesn't break down the homicide rates into types, and says nothing about why gun homicide rates dropped precipitously but others stayed the same.