Graphs of political book purchasing habits of amazon readers. These graphs demonstrate echo chambers in our society wherein the left talks to itself and the right talks to itself. There are a very small number of books that people on both sides read relative to the slew of books that are only read by people on a particular side. This is an old meme, but the graph has been updated recently. I memed an old version of this, but I had trouble finding it today. So, I'm rememing.

Political Books -- Polarized Readers -- May 2004