J.K. Rowling won four platinum awards, one for each of her best-selling Harry Potter novels.
The author didn't attend Friday's ceremony in London but asked her publisher, Nigel Newton, to deliver a message of thanks.
"Despite what you may have read, and probably to Nigel's immense relief, I am happily incarcerated in a rather chilly Edinburgh, busily writing Book Five," Rowling's message said.
The British book industry created the prizes, modeled after the music industry's gold and platinum records. Platinum awards recognize sales of more than a million books.