This from The Guardian UK -
Book experts said that sales are likely to have been boosted by commuters eager to re-read the hugely successful franchise but less keen to be seen in public reading a children’s book.
E-reading devices such as Kindles and iPads allow a person’s reading matter to remain anonymous.
All seven Harry Potter books were released in digital format on the Pottermore website on March 27.
After just three days the site saw sales of “over £1 million”, according to Charlie Redmayne, the chief executive of Pottermore.
Mr Redmayne told Radio Litopia, a literary radio station, that sales were ahead of “anything I’ve ever seen for ebook sales”.