Prince Harry's memoir publisher said the Duke's book was the fastest-selling non-fiction book of all time.
The Duke of Sussex’s autobiography recorded sales figures of 400,000 copies so far across hardback, ebook and audio formats on its first day of publication, according to publisher Transworld Penguin Random House.
Larry Finlay, the publisher's managing director, 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]."
The memoir had been leaked to the world five days early in Spain, and was extensively quoted in the Duke's jaw-dropping glut of TV interviews.
The eagerly-anticipated 416-page memoir certainly hasn't disappointed with its spicy revelations of life within the Royal Family.
According to Penguin Random House, Spare tells the Duke's story with 'raw, unflinching honesty', chronicling his journey from 'trauma to healing'.
Among the book's claims included King Charles pleading with his warring sons not to make his 'final years a misery'.
Speaking ahead of the book's release, Harry claimed his family 'have shown absolutely no willingness to reconcile' - but a source has slammed the Duke's accusation as 'unadulterated nonsense'.
Yet despite all the ill-feeling, Harry also said he would 'like to have my father and brother back'.
Explosive details from the memoir, including that Harry's brother Prince William allegedly assaulted him in a row over Meghan Markle, have caused shockwaves. But, the Royal Family has yet to officially comment or respond.
Bert's Books in Swindon meanwhile made a tongue-in-cheek gesture hinting at the royal family fallout after copies of the hotly-anticipated memoir were arranged alongside the punchily-titled fiction accompaniment.
Bert's Books in Swindon meanwhile made a tongue-in-cheek gesture hinting at the royal family fallout after copies of the hotly-anticipated memoir were arranged alongside the punchily-titled fiction accompaniment.
How To Kill Your Family was originally released 18 months ago, but was last year's bestselling book for the independent shop.
Bearing uncannily similar themes to the non-fictional scandal currently embroiling the royals, the novel tells of a millionaire's daughter who vows to exact revenge on him and all her other paternal relatives after he rejects her dying mother's pleas for help.
Bert's Books tweeted a picture of the simple display on Tuesday morning.
"Anyway, we do have some spare copies of Spare if you want one," the shop quipped.
