Well, what do you know? the best-selling book over the last decade was E.L. James’s 50 Shades of Grey, which which sold 15.2 million copies from 2010 through 2019. It was originally self-published as a Kindle ebook and print-on-demand publication in June 2011; the publishing rights were acquired by Vintage Books in March 2012. Smart move. I wonder what they paid for them.