(Hey, everyone else seems to have written one; why buck the trend?)
I'm not the first to observe that there are really two books inside the covers of Army of Davids, each occupying about half the page count. In the first, Reynolds speaks of what he knows first hand: citizens' media, the forces that have created them, and much of the social impact. As living proof that you don't have to build a portal to wield influence in the Web, Reynolds brings the credibility that he can surf that particular set of waves. In the second half of the book, he opines on matters such as space, nanotechnology, and biotech, where he has no direct experience. Reynolds is not a technologist or businessman, and it shows.