The debut book by racy publishing phenomenon EL James, Fifty Shades Of Grey, has become the first to sell more than one million copies on Kindle.
Online retailer Amazon.co.uk says James has already become its best-selling author of the year and the book is the biggest Kindle ebook yet.
James - whose real name is Erika Leonard - has had colossal sales for her erotic fiction books, with the paperback version of her debut achieving the UK's highest weekly sale for a paperback.
Amazon said the Kindle edition of Fifty Shades was outselling the print book at a rate of more than two to one.
Her trilogy of saucy Grey books was published in March. The film rights have already been snapped up.
Gordon Willoughby, director of EU Kindle, said: "EL James's books have become both the fastest-selling and the best-selling series ever on Kindle - that's an exceptional achievement for a debut novelist and we're excited to see her pass the one million sales milestone."
The print versions of her books - the others are titled Fifty Shades Darker and Fifty Shades Freed - take the top three places in Amazon's bestseller lists.
James's husband Niall Leonard has also landed a publishing deal for his debut novel, a thriller called Crusher aimed at young adults.
Last week, the paperback of Fifty Shades sold more than 200,000 copies, to establish a new weekly record.