The fine folks at Amazon have constructed a "heat map" showing the kinds of political books that people are buying across the country. The more conservative a state's literary tastes, the more red it appears on the map. The more liberal the reading habits, the bluer the state gets. Here's the result:

Conservative authors are selling more books. That's true in Mississippi, but it's also true in Connecticut. And it looks like Amazon's methodology is, if anything, understating matters. They count Jonathan Haidt's "The Righteous Mind" as a "blue book." I've read "The Righteous Mind," and it is, if anything, a scolding of liberals. They also count "Globalization: A Very Short Introduction" and Robert Caro's most recenet biography of LBJ as blue books, which seems odd. None of the top 20 "red books" struck me as similarly misplaced. So if you correct for the outliers, the map would be even redder.

Some possible explanations:

1. Conservatives are more likely to read political books than liberals are.

2. Conservatives are more likely to read partisan political books than liberals are.

3. Conservatives are better at writing political books that people want to read than liberals are.

4. Liberals are focused on consolidating their control of Hollywood rather than making gains in the publishing industry. (Yes, this is a joke.)

5. It's easier for the opposition to sell books. If you look at the "red books," they're largely about Obama. The top "blue book," meanwhile, is Howard Zinn's "A People's History of the United States." It would be interesting to see what this map looked like in 2004.

My guess is that #5 is the big mover here, with #1 and #2 playing a role as well. But feel free to correct me in comments.