The Duke of Sussex's memoir has become the fastest selling non-fiction book ever as Spare was finally released on Tuesday.
The book, which has hit the headlines over the past week after it went on sale early in Spain, was boosted into the record books with 400,000 hardback, e-book and audio format copies being snapped up, its publisher said.
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In comparison, Andrew Morton's book, Diana: Her True Story sold five million copies in 1992.
Prince Harry has shared a number of shocking revelations in his memoir, including details of a physical altercation with brother, Prince William, and why he felt that his stepmother, Queen Consort Camilla, was "dangerous".
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© Photo: RexPrince Harry's interview with Tom Bradby aired on Sunday
Larry Finlay, managing director of Transworld Penguin Random House, said: "We always knew this book would fly but it is exceeding even our most bullish expectations.
“As far as we know, the only books to have sold more in their first day are those starring the other Harry (Potter)."
Harry's interviews with ITV's Tom Bradby and CBS' Anderson Cooper aired on Sunday night ahead of the book release.
During his ITV appearance, the Duke claimed that he had never accused the royal family of racism, and that he does not think they are racist.
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Meanwhile, Harry told Good Morning America on Monday that there has always been competition between him and William, and referred to the British press's part in it.
He said: "They pitch the Waleses, which Kate and William are now, against the Sussexes, me and my wife.
"They always pitched us against each other. They pitch Kate and Meghan against each other."
Asked if he thought this then made the two women "go against each other", he said yes "without question".
The Duke will also appear on The Late Show with Stephen Colbert in the US on Tuesday evening.
