The memoirs of Britain's Prince Harry

Prince Henry Charles Albert David Mountbatten-Windsor, Duke of Sussex (in English Henry Charles Albert David), "Spare" ("Spare") is the fastest-selling non-fiction book in the United Kingdom, according to its publisher, reported Reuters.

In its first day on the market, 400,000 copies of the biography were sold in print, e-book and audio formats.

"We knew this book would take off, but this has exceeded our wildest expectations," Larry Finley, managing director of Transworld Penguin Random House, said in a statement.

"To our knowledge, the only books that have sold faster on their first day on the market are the Harry Potter novels," the statement said.

Publisher figures are based on UK market sales only.

The memoir has attracted worldwide interest because of Prince Harry's revelations and accusations

Prince Henry Charles Albert David Mountbatten-Windsor, Duke of Sussex (in English Henry Charles Albert David), to his father King Charles III

Charles III, full name Charles Philip Arthur George Mountbatten-Windsor, is a king and statesman, his stepmother Camilla and his older brother Prince William

William Arthur Philip Louis Mountbatten-Windsor, Duke of Cambridge (English: William Arthur Philip Louis) is a member.

Prince Harry, with more revelations about the British royal family, viciously attacked Camilla

Prince Harry

Prince William

Charles III