Worldwide sales of A Song of Ice and Fire, the book series on which the Game of Thrones TV series is based, have passed 70 million.
Sales of A Song of Ice and Fire hit 58 million in April 2015, indicating that the series has sold an additional 12 million copies in just the last year. With no new novel released in that time, that is a remarkable achievement and a reflection of the success of both the books and the TV show helping drive sales.
This month marks the 20th anniversary of the publication of A Game of Thrones. It is also approximately 25 years since George R.R. Martin started writing the series and the sixteenth anniversary of the publication of A Storm of Swords (which I read on release, something I will forever be grateful for). I will be writing a more in-depth article on the anniversary shortly.
How do Martin's sales compare to other SF and fantasy authors? Quite favourably*:
JK Rowling: 450 million
Stephen King: 300 million
JRR Tolkien: 300 million
Stephanie Meyer: 250 million
Anne Rice: 136 million
CS Lewis: 120 million
Edgar Rice Burroughs: 100 million
Sir Arthur C. Clarke: 100 million
Suzanne Collins: 100 million
Andre Norton: 90 million
Sir Terry Pratchett: 85 million
Robert Jordan: 80 million
George R.R. Martin: 70 million
* Yes, this list is out of date. An update is in the planning.