The much-publicised book sold 467,183 copies in its first week, according to official figures from Nielsen BookData.
The book, which was written with celebrity ghostwriter JR Moehringer, went on sale on 10 January.
Most of the revelations in the book leaked early after some copies went on sale in Spain several days before the official publication date.
But that does not appear to have damaged sales of Spare. The only books to have enjoyed higher first-week sales since Nielsen's records began were four Harry Potter novels and Dan Brown's The Lost Symbol.