It's a difficult question to answer because the world's best-selling novels change over time. According to some reports,"Harry Potter and the Sorcerer's Stone" is the world's highest-selling novel with more than 70 million copies sold. However, this number might vary according to different statistics and standards. There were also other famous novels such as The Catcher in the Rye, 1984, and Miserable World, which were once among the top selling novels in the world.