The latest instalment in Fifty Shades author EL James's sadomasochistic saga has smashed UK sales records, selling more than 647,000 copies in three days.
The new book, called Grey, is a retelling of the first novel in the hit series about an affair between mysterious tycoon Christian Grey and lover Anastasia Steele, from the point of view of its title character.
Figures released by publisher Arrow Books show sales of 385,972 physical copies and 261,429 ebooks - a total of 647,401 - giving the biggest first week sales for an adult book.
The previous UK record holder was Dan Brown's The Lost Symbol, which sold just under 551,000 copies in five days.
Cornerstone managing director Susan Sandon said: "We've had magnificent support from across the trade. The excitement and enthusiasm that Grey's publication has generated is totally irresistible and I am delighted with these early results."
The book was also a huge hit in the US where it has sold more than a million copies since Thursday.
The story, set over a month from May 9 to June 9 2011, is described as "a fresh perspective on the love story that has enthralled millions of readers around the world" and the story of the title character's battle with the "compulsion to control" and "dark sexual desires".
It starts with Grey having a nightmare about his childhood before he meets Steele, who is described as arriving in a "a whirl of long chestnut hair, pale limbs and brown boots".
The story of his pursuit of Steele and James's raunchy description of their S&M relationship will be familiar to readers of her first three books, which all topped best-seller lists.
The book is dedicated by James to her readers with the words: "Thank you for all that you've done for me. You rock my world every day," and includes thanks to a host of people including those who guided the author through "an education in soil science", "behavioural health" and "guidance in flying a helicopter".
It made headlines ahead of publication when it was reported that a finished copy had been stolen.
The publishers vowed to continue to investigate the theft despite police saying there was no evidence a crime had been committed.
Jamie Dornan played Grey and Dakota Johnson was his lover in the hugely successful film version of the story.
The Fifty Shades trilogy - Fifty Shades Of Grey, Fifty Shades Darker and Fifty Shades Freed - has sold more than 125 million copies around the world.
It has made James a millionaire many times over. This year's Sunday Times Rich List estimated her fortune at £75 million.