A Picture of Political Word Influence

This site has an interesting analysis of the purchase pattern of top moving political books. The influential books are those that connect distinct political philosophies - the ones read by people in both the "liberal" and "conservative" camps (though I think the break-out is pretty inaccurate when you actually talk to people). The site also has a white paper by the owner on the subject of book networks as well as some links to articles in the popular press.