The big difference between this network map and the previous two are the number of books in the middle. The release of two popular middle books, colored purple, expose a further network of middle books. Ghost Wars reveals one group of middle books, while The Rise of the Vulcans reveals a second group. Yet, the increase in boundary-spanning books does not indicate a shift in the political landscape. The three network maps are not that different within common statistical limits. The division between left and right remains strong. Network metrics, as well as the visuals, show two dense clusters with high preference for homogeneous choices. Echo chambers, on the right and left, remain amongst book readers in America.