Harry Potter And The Cursed Child has become the fastest-selling book in the UK this decade, selling more than 680,000 copies in its first three days.
It beats Fifty Shades Of Grey, which sold 664,478 copies in one single week in 2012.
The script, which tells the story of the newly-opened West End show, has also sold two million copies in two days in the US and Canada.
Ellie Berger, President of Scholastic Trade, said in a statement: “Eager fans of all ages gathered at midnight parties in bookstores and libraries to get their copies of Harry Potter and the Cursed Child, bringing communities together to celebrate the magic of reading and the power of great storytelling.”
The book is currently on track to gross the second biggest single-week sales for a book since records began. The number one book in that category is Harry Potter And The Deathly Hallows, which sold 1.8 million copies in its launch week in 2007.
A sequel to the Harry Potter spin-off movie Fantastic Beasts and Where To Find Them has been given a release date of 2018, according to Warner Bros Pictures.
Although the first Fantastic Beasts movie, starring Eddie Redmayne, is yet to be released, director David Yates has confirmed that he will be returning to direct the sequel, having already read the script written by JK Rowling.