It's been coming for a while, but now the latest sales figures appear to confirm it's happened: sales of George R.R. Martin's A Song of Ice and Fire fantasy series have surpassed those of Robert Jordan's Wheel of Time sequence, meaning that A Song of Ice and Fire is now the most popular epic fantasy series published since The Lord of the Rings (at least arguably).
Of course, with only five volumes available compared to The Wheel of Time's fourteen, A Song of Ice and Fire has had far more readers than Wheel of Time for some time (roughly 18 million to 6.5 million), but the overtaking in terms of outright sales remains a significant and impressive achievement.
The first Wheel of Time novel, The Eye of the World, was published in 1990 by Tor Books and was a massive hit, shifting 40,000 copies of the first-run hardcover. The later novels did even better, and every book in the series from The Path of Daggers (1998) through A Memory of Light (2013) hit #1 on The New York Times bestseller list in the week of release. As of Robert Jordan's sad passing in 2007, the series had sold 44 million copies in North America and roughly 70 million worldwide. Brandon Sanderson completed the final three books in the series, with global sales of the series surpassing 80 million by 2014 (according to Jordan's French publishers) and increasing further. Current estimates suggest sales of between 85 and 90 million.
A Song of Ice and Fire, in contrast, was a slow but steady grower. The first book in the series, A Game of Thrones (1996), did not sell well on release and only started doing better with the paperback edition (ironically, apparently due to a Robert Jordan cover quote, with George R.R. Martin himself crediting a cross-pollination of fans of both series for helping increase his story's popularity). The second novel in the series, A Clash of Kings (1998), brushed the lower reaches of the bestseller lists but it only started hitting the big time with the third volume, A Storm of Swords (2000), which reached #11 on the New York Times list.
By the time A Feast for Crows was released in 2005, the popularity and profile of the series had boomed and it had sold over 5 million copies. Despite increasing delays between books, the popularity of the series continued to increase. As of the release of A Dance with Dragons in 2011, the series had sold well over 12 million copies worldwide. That same year, the HBO TV series Game of Thrones, based on the books, was launched and this resulted in a titanic explosion of sales. A Song of Ice and Fire sold over 9 million copies in 2011 by itself and sales continued to accelerate dramatically. Overall sales of the series hit 58 million in April 2015 and 70 million in August 2016, on the twentieth anniversary of the first book's publication.
Industry sales figures now show that A Song of Ice and Fire has sold 45 million copies in the United States alone. The publishing rule of thumb is that global sales once a book series has exceeded c. 20 million copies (with a film or TV adaptation available) are more than double that of the US. We can therefore declare with overwhelming confidence that A Song of Ice and Fire has sold more than 90 million copies worldwide, putting Martin just ahead of not just Jordan, but also the late Sir Terry Pratchett, whose 41 Discworld novels have sold more than 85 million copies worldwide since 1983.
Remarkably, A Song of Ice and Fire's success has spread to the spin-off material, with companion volume The World of Ice and Fire reportedly selling more than 1 million copies since its publication in 2014 as well. Sales of The Wheel of Time's first companion volume (1997's World of Robert Jordan's The Wheel of Time) were apparently much more modest and of the second volume (2015's Wheel of Time Companion) very poor in comparison.
This impressive achievement may only be temporary, however. Amazon is developing a Wheel of Time television series and we can expect an impressive boom in sales for that series when that finally hits the air (most likely in 2020 or 2021), whilst sales of A Song of Ice and Fire are likely to start tailing off once the TV series stops airing next year. And of course, although ASoIaF's achievement is noteworthy, it still has a way to go to catch up on J.K. Rowling's 600 million copies of Harry Potter sold.
The scale of A Song of Ice and Fire's achievement should not be underestimated, however, and this will explain the increased eagerness the publishers have to get their hands on The Winds of Winter.