Posted by Jay Livingston
Tyler Cowen asks his readers to guess the best-selling book of all time (“And I mean the best-selling real book, not linked to either religion or communism?”)
Here is his answer:
Charles Dickens, A Tale of Two Cities, two hundred million copies.Note that Tyler tactfully refers to Baden-Powell’s 1908 classic in the generic rather than by its actual title, which is so much more delightfully ambiguous: Scouting for Boys.
Next in line is Baden-Powell's Boy Scouts book and then Lord of the Rings.
(Wikipedia has the full list.)