Harry Potter and the Cursed Child Parts I & II has officially become the fastest-selling book for almost a decade, and the fastest-selling play script of all time.

The title shot straight to number one in the UK and Ireland following its publication on July 31st - selling almost 850,000 print copies in the UK and over 35,000 print copies in Ireland in its first week.

CEO of Little, Brown Book Group David Shelley said the sales figures were "way beyond" their expectations.

"It is a testament to the passion readers have for J.K. Rowling’s Wizarding World, as well as to the amazing reception the play itself has had."

...The Cursed Child is the script book of an original new story by J.K. Rowling, John Tiffany and Jack Thorne, and is a new play by Thorne.

The book currently on sale is a 'Special Rehearsal Edition', containing the complete script used by the original West End production during the play’s summer preview period, including stage directions.

The 'Definitive Collector's Edition' will arrive next year.