That is: THE HOBBIT ranks fourth on their list, with 100,000,000 copies sold. That's one hundred million copies. Which is a lot of books. But it's a distance second among Tolkien's works on the list, THE LORD OF THE RINGS having sold half again as much: 150,000,000 copies (whether sets or individual volumes they did not say). That's a quarter of a billion copies altogether for those two books.
I'm reminded of something Janice said, years ago as we were leaving a Half-Price Books up on the Brown Deer Road in Milwaukee, about imagining how our civilization wd appear to archeologists of the distant future, who wd decide that we had v. few books but really, really liked them.
I'm also reminded of the famous Locus poll (circa 1987/88, I think) of all-time favorite fantasy works, in which Tolkien's THE LORD OF THE RINGS came in first. Followed by J. R. R. Tolkien's THE HOBBIT as number two. Followed, I think by Le Guin's A WIZARD OF EARTHSEA as a rather distant third. The poll's compiler I remember went to lengths to point out that the winner of the fantasy poll outperformed the winner of the science fiction poll they ran at the same time (this being after all a science fiction journal) by a magnitude of degree.
The dual placement of both books on the Wikipedia list, which together take up a third of the list of all books that have sold 100 million or more copies, is what's really staggering, and re-inforces once again that THE HOBBIT has an audience of its own. If Tolkien had written only THE HOBBIT, I'd argue, he wd still be remembered as one of the great writers of his time.
Not just King of the Mountain: without him, there'd be no recognized genre of fantasy literature, and the people who wrote what we'd call modern fantasy wd be talented eccentrics following their individual muses, like James Branch Cabell, E. R. Eddison, and Hope Mirrlees.
All hail not the King Under the Mountain but The King Up On The Mountain, for letting us share the view.***
--writing from what turns out to be Grand Prairie, Texas
***(cf. Tolk's allegory of the tower in The Monsters & The Critics).
UPDATE (Jan. 27th): thanks to Allan for pointing out that 250,000,000 is a quarter-BILLION, not a quarter-million, as I'd mistyped. I've corrected this above. Thanks Allan! -- JDR