5. The World Almanac and Book of Facts (2003) – 73.5 Million
By World Almanac Books
First published in 1868, this book has seen itself being reprinted in year by year basis. This is a comprehensive collection of themes touching almost every aspect of human life. This became a favorite of many people across the world making it to have a high demand. Since then an estimated 73.5 million copies have been sold making it one of the best selling books of all time.