Boxing up a political map: An worker loads boxes. Blue books head for Maryland. (AP Photo/Ross D. Franklin) has released what it calls an Election Heat Map showing which states lean more heavily to buying conservative-leaning books or liberal ones. Red = conservative, like Virginia. Blue = liberal, like Maryland. Beige = a tie, like Pennsylvania. The map is updated daily.

How is Amazon doing this?

“The Amazon Books Editorial team pulled extensive lists of best-selling books in relevant categories and vetted them using a variety of tools for clear partisan leaning, separating them into red and blue categories,” the company says. “Many books, of course, have no clear political bias, and therefore were not included.”

(You can learn more about the methodology here.)

There are obviously many holes in this type of analysis, most notably that the map doesn’t factor in books bought elsewhere. (Yes, people still buy books elsewhere — at Barnes & Noble, Politics & Prose, Target and even Costco, where book tables are always loaded with political best-sellers aimed at both sides of the aisle.)

But the map still makes for fascinating clicking. You can select each state and see the top 10 political books — blue and red — being shipped in that state’s direction.

In Maryland, 52 percent of books shipped here are blue.

The best-selling blue book is “The Price of Inequality: How Today’s Divided Society Endangers Our Future,” by Nobel Prize economist Joseph Stiglitz. The best-selling red book: “Killing Lincoln: The Shocking Assassination that Changed America Forever,” by Bill O’Reilly and Martin Dugard.

(I’m not sure why a Lincoln killing book is classified red, but O’Reilly probably has something to do with it.)

As for the rest of the country, Amazon says 56 percent of books sold are red, 44 percent are blue. Those sales roughly correlate to political ideology representation in the country, with conservatives topping moderate and liberals, according to Gallup.

Should Maryland’s book reading habits turn red, I’ll update you. Don’t expect such an update soon — or ever.