The new novel, Grey, features the same story as James' first book but it has been rewritten from the point of view of kinky businessman Christian Grey, played by Jamie Dornan in the big screen adaptation.

It was universally panned by critics following its release last week (ends21Jun15), with reviewers condemning James' writing style as "comical" and branding the book a blatant "cut and paste" rehashing of Fifty Shades of Grey.

However, the critical mauling failed to dent the novel's soaring sales and it has broken records in the U.K. by selling a staggering 647,401 copies, physical and digital, in just three days.

The figures make it the fastest selling book in Britain since records began, trouncing the previous record set by Dan Brown's The Lost Symbol, which sold nearly 551,000 copies in five days following its release in 2009.

Grey also proved a big hit in the U.S., selling around 1.1 million copies in its first four days of release.