The book, Harry Potter and Half-Blood Prince was launched at 12.01am on Saturday morning. A number of retailers, including Asda, Tesco, WHSmith and Waterstones, opened stores in the early hours of the morning to take advantage of the huge demand for the book.
Few sales figures have been released yet, but Asda said that it sold nearly 300,000 copies over the weekend. This equates to 11 copies a second.
However, a spokesowman for WHSmith said that its stores were selling the book at a rate of about 13 copies a second.
'All of the shops had fantastic queues of people outside.' She said. 'We still think this is going to be the biggest Harry Potter book yet.'
A spokeswoman from Waterstones concurred that Potter fans were out in force from the minute the book was on sale. She confirmed that the bookseller's Oxford Street store in London had attracted a mile-long queue of about 2,500 people.
The retailer's Edinburgh Princes Street store had a queue of 700 people waiting outside to grab a copy of the book.