Sales of the Harry Potter books have reached the quarter of a billion mark.
The five books by JK Rowling have been translated into 60 languages and sold in more than 200 countries.
Rowling's agent, Christopher Little, also told Reuters that the author has begun work on the sixth instalment but no release date has been set.
The big screen adaptation of the third Harry Potter book, 'The Prisoner of Azkaban', is due for release next summer.
