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.
Are you a Fifty Shades fan? Take a look at HuffPost's guide to bondage for beginners...
"Bondage" covers a very wide spectrum of sex acts, and can mean something different to every person," says Rochelle Peachey, couples counsellor, author and founder of transatlantic dating site I Love Your Accent Is it being blindfolded and maybe tying your wrists with silk scarves or something way more elaborate? Or something you would like to add to your sex life or is this something you like to do all the time? Whatever it is, as long as you both agree on the boundaries, anything goes. Bondage isn't all whips, dungeons and medieval torture but make no mistake they do play a huge part for many."
"There are no rules to follow, you make the rues together," says Rochelle Peachey. "Create a special word in case it gets too much for you, something sexier than screaming "get off me".
"Although it's often more tempting to play sex games when you're feeling a bit tipsy, it's best not to try bondage when you're under the influence of drink or drugs, as you might misjudge how tightly to tie the knots or, as the restrained person, be unable to establish your comfort levels in an accurate way," says Emily Dubberley, author of The Field Guide to F*cking.
"Take a DIY approach to bondage if you're on a budget. Clingfilm can be used to wrap around your lover's wrists, and if you use a single layer, it's easy enough to snap. You can get kitsch and use liquorice bootlaces to bind your lover's wrists, go for a cheap option and use toilet paper," advises Emily Dubberley.
"With bondage, there's a risk you can tie your partner too tightly and cause damage to their nerves. To avoid this, when someone is restrained by their wrists or ankles make sure that you check their extremities (hands and feet) regularly to ensure that they're not going cold (which is a sign that you've blocked their circulation). If the extremities do feel cold, untie your partner immediately and massage their hands or feet to help restore blood flow," explains Rochelle Peachey.
"Make sure that you keep a pair of scissors to hand, so that you can release your partner quickly if the need arises. Similarly, if you're using handcuffs, keep two sets of handcuff keys near by (it's always best to have a spare just in case you lose the first set)," says Emily Dubberley.
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 1.8m 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.
10 reasons to get busy under the sheet tonight...
Besides being fun and pleasurable, sex also offers many health boosts many of us take for granted. Take a look at these surprise benefits of having regular sex...
According to research from Wilkes University, making love twice a week releases an antibody called immunoglobulin A or IgA, which helps protect the body from infections and illnesses. Other research suggests that frequent ejaculations in men reduces the risk of prostate cancer later in life. According to the British Journal of Urology International, men who ejaculate five or more times a week, had a lower risk of prostate cancer.
It doesn't take an expert to connect an energetic love making session with burning calories. Just thirty minutes of action under the sheets burns off around 85 calories. After 42 half-hour sessions, you could burn 3,570 calories, which is the equivalent of 1lb in weight. By having sex three times a week for a year, you could burn off the equivalent of 5lbs a year. Who needs a diet?!
During sex, a hormone called oxytocin is released when the body climaxes, which increases the level of endorphins that acts like natural a pain relief. This causes the body to relax. Many notice their aches and pains, like swelling, inflammation, headaches and menstrual cramps, disappear after sex and gradually improve with regular action.
Women who have regular orgasms are generally more relaxed, less depressed and mentally, physically and emotionally satisfied. Regular sex also helps the body sleep better as it relieves tension plus it helps the brain produce serotonin - the chemical that gives the body a 'mood' lift and is commonly found in antidepressants.
Regular sex releases a surge of plethora chemicals into the body, also known as the 'happy hormones', and they contain testosterone. As we age, the level of testosterone decreases, so the more sex you have, the more your hormone levels increases. This surge of hormone help keep bones and muscles healthy - plus it keeps skin looking plump and youthful. In women, regular sex also helps keep the pelvic floor muscles healthy, which decreases the chances of not-so-sexy incontinence later in life.