Prince Harry's memoir "Spare" has become the UK's fastest-selling non-fiction book ever, the book's publisher said on Tuesday, having sold 400,000 copies across hardback, ebook and audio formats.
"We always knew this book would fly but it is exceeding even our most bullish expectations," Transworld Penguin Random House Managing Director Larry Finlay said in a statement.
"As far as we know, the only books to have sold more in their first day are those starring the other Harry (Potter)."
The publisher said this was based on British sales.
Harry's book, whose Spanish language edition went on sale earlier than planned by mistake, officially went on sale on Tuesday, with eager readers heading to bookshops to get their copy of a book that contains intimate revelations about the British royal family.
The book has garnered attention around the world due to its disclosures about Harry's accusations about his father King Charles, stepmother Camilla and elder brother Prince William.