The latest instalment in Fifty Shades author EL James's sadomasochistic saga has proved a hit with readers, selling more than a million copies in the US since Thursday.
The new book, called Grey, is a re-telling 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 from the US show it sold 1.1 million copies there and UK sales data, to be released today, are expected to confirm its best-seller status.
The story, set over the course of a month from May 9 2011 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 even ahead of its publication when it was reported that a finished copy had been stolen.
The publishers vowed to continue to investigate the theft of a copy of the unpublished book despite police saying there was "no evidence" a crime had been committed.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.