Racy literary hit Fifty Shades Of Grey has become the fastest paperback to hit one million sales - and smashed its own one-week sales record.
The erotic tale, the first in a trilogy by EL James, reached seven-figure sales in only 11 weeks. It hit the target 25 weeks faster than the previous record-holder, Dan Brown's The Da Vinci Code.
And the book has shattered the seven-day sales record for an adult paperback which it set only last week - by selling almost twice as many copies.
Fifty Shades shifted 397,889 paperbacks in a week, bettering the 205,130 it established just a few days earlier.
But both of James's follow-up titles also bettered that figure, according to the latest figures from Nielsen BookScan which compiles book industry data.
Fifty Shades Darker sold 245,801 while Fifty Shades Freed sold 212,832.
Until this month, the adult paperback record was another of those held by The Da Vinci Code with a one-week sale of 141,156 copies.
Fifty Shades has also beaten the one-week sale of JK Rowling's children's book The Tales Of Beedle The Bard, which rang up 367,625 sales when it was released in 2008.
It gives the book a new record for the biggest weekly tally for a paperback in the UK.
Sales have been similarly huge for digital copies of the books. Earlier this week Amazon announced that Fifty Shades has become the first title to sell more than one million copies for its Kindle device.
Industry magazine The Bookseller has reported that physical sales of James's books totalled £3.9 million last week, and her three titles outsold the rest of the entire top 50 bestsellers by more than two to one.
Despite the colossal sales so far, Fifty Shades is still some way off the overall weekly UK sales records. One of Rowling's Harry Potter titles sold 1.8 million hardback copies in a week, and Brown's The Lost Symbol is the top-selling adult book, with almost 551,000 copies, again in hardback.
Mother-of-two James - whose real name is Erika Leonard - has already sold the film rights to Fifty Shades Of Grey, which began as an online tale.
Her books follow the erotic adventures of a young graduate and her submissive relationship with a handsome billionaire.