You may have seen the maps showing how the red and blue fare on votes and campaign contributions. But have you checked out the Amazon.com map on political book sales?
It may not be especially illuminating at any single moment, especially when a few hot new titles might push things in one direction or another. But over time, it could provide some insight into how political books match up with local politics.
You'll notice, for example, that while Republican-leaning books are leading generally in the Northwest (as in most of the country) at the moment, that Idaho (buying 64% red to 36% blue) is much more so than Washington or Oregon (both 54% red/46% blue).