Harry Potter & The Cursed Child Parts One and Two sold more than 2 million copies in 48 hours in just it’s North American market. The eighth Harry Potter story is a script for a theatrical production written by J.K. Rowling along with John Tiffany and Jack Thorne. The first printing included 4.5 million copies. (Source: GalleyCat)

Although its predecessor Harry Potter & The Deathly Hallows sold 8.3 million copies in 2007 during its first 24 hours, Harry Potter & The Cursed Child Parts One and Two is on track to be the bestselling book of 2016. (Source: Mashable)