There are 2.9 million Google entries for The Da Vinci Code. The book has sold over 18 million copies in 44 languages.
Its author, Dan Brown, is said to have earned more than £140 million (€200m+) in the process.
The basic plot? A murder in the Louvre gallery in Paris and clues in da Vinci paintings lead to the discovery of a religious mystery protected by a secret society for 2,000 years - which could shake the foundations of Christianity.
The book is due to be made into a film, starting in May.
The creator of 24, Joel Surnow, the US-made conspiracy theory TV thriller starring Kiefer Sutherland, wanted to use the book's storyline for his third season of the serial and put the idea to his boss, producer Brian Grazer. But Dan Brown turned down Grazer's blandishments.
Soon after, Sony Pictures paid $6 million for the book and hired Grazer as producer.
Russell Crowe was considered for the role of hero Robert Langdon. The film will now feature Tom Hanks instead.