I found this fact interesting about books
I knew the Koran and the Bible were two of the best-selling books throughout history. The exact copies sold or in existence is a highly debated topic because of their historical longevity and lack of sales records to pinpoint exact numbers.
When I was looking through the best selling individual books Wikipedia page I was extremely surprised to see Don Quixote as the number one book(when excluding the Bible and Koran) with 500 Million Copies sold.
Does this surprise you?