1. Don Quixote by Miguel de Cervantes 500 million copies sold
2. A Tale of Two Cities by Charles Dickens 200 million copies sold
3. The Lord of the Rings by J.R.R. Tolkien 150 million copies sold
4. The Little Prince by Antoine de Saint-Exupery 142 million copies sold
5. Harry Potter and the Sorcerer’s Stone by J.L. Rowling 107 million copies sold
6. And Then There Were None by Agatha Christie 100 million copies sold
7. The Dream of the Red Table by Cao Xueqin 100 million copies sold
8. The Hobbit by J.R.R. Tolkien 100 million copies sold
9. The Lion, the Witch and the Wardrobe by C.S. Lewis 85 million copies sold
10. The Da Vinci Code by Dan Brown 80 million copies sold

Source: FactRetriever.com