In figures released by the book's publisher, Penguin Random House, it was revealed that the memoir had broken their personal record largest first-day sales total for any nonfiction book in its history, with nearly one and a half million copies being shifted across the United Kingdom, United States and Canada.
WATCH: The key revelations from Spare
When the book was announced, two million copies were printed in the United States alone, and it has now returned to the printworks for extra copies to be printed in order to meet demand.
Harry's memoirs were published in 16 different languages and was due to be launched worldwide simultaneously, although it ended up leaking in Spain a few days ahead of its Tuesday release.
Gina Centrello, President and Publisher of the Random House Group, said: "While many books by public figures can be fairly categorized as 'celebrity memoir,' SPARE is not that.
"Vulnerable and heartfelt, brave and intimate, SPARE is the story of someone we may have thought we already knew, but now we can truly come to understand Prince Harry through his own words."
The book has broken sales records
She added: "Looking at these extraordinary first day sales, readers clearly agree, SPARE is a book that demands to be read, and it is a book we are proud to publish."
The book has divided opinion since its release with many praising its unflinching account, while others highlighted potential inaccuracies inside its pages.
In one honest extract, the Duke of Sussex opens up about a time that he ended up snapping at his wife, Meghan Markle.
Harry recounted an argument between him and Meghan
"Maybe the wine went to my head. Maybe the weeks of battling the press had worn me down," he wrote, referencing one night at home in Nottingham Cottage. "For some reason, when the conversation took an unexpected turn, I became touchy. Then angry. Disproportionately, sloppily angry."
HELLO! talks all things Spare
The Duke put the outburst down to "cultural differences" and a "language barrier", admitting interpreted one of Meghan's comments, "the wrong way".
Although Prince Harry does not reveal the topic of discussion, he recalled how he spoke to her with "cruel" and "harsh" words. "I was also just over-sensitive that night. I thought: 'Why's she having a go at me?' I snapped at her, spoke to her harshly [and] cruelly. As the words left my mouth, I could feel everything in the room come to a stop."
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