What is the most popular book?

Religious texts such as The Bible and The Qur'an are typically the books that are most often printed and distributed around the world.

Religious texts aside, the book to have sold the most copies is A Tale of Two Cities by Charles Dickens which has sold approximately 200 million copies.

Not far behind this is The Lord of the Rings by J. R. R. Tolkien which has sold approximately 150 million copies.