“Best-selling” refers to the estimated number of copies sold of each book, rather than the number of books printed. Comics not included in this list. The books are listed according to the highest sales estimate as reported in reliable, independent sources.
Also, it is worth noting that some religious and political books such as The Bible, Quran, and Quotations from Chairman Mao are believed to have more than a billion copies each in existence. However, sales numbers for these books are nearly impossible to track because many are given away by churches or governments.