4. The Hobbit / J.R. Tolkien
(Approx. 100 million copies)
In 1937, quite a long time before the whole world asked itself questions about the magical world beyond the wall, dragons, and dark magic, JR Tolkien, a professor of linguistics, published a short book about Bilbo Baggins, the hobbit who liked to stay at home but gets swept away on a strange and exciting adventure, and incidentally also finds a small ring – which will later be revealed to have tremendous power.