Since this thread is still a little active, for the heck of it I searched again to see if the answer was out there. It was not. But I happened to come up with this Publishers Weekly page on the bestselling books for 2014, for those who might like to look at it:
The Bestselling Books of 2014
The entire list is interesting, but here are the two entries the board cares about.
Revival sold just under 345,000 copies.
Mr. Mercedes moved a little over 308,000 copies.
I guess, by the way, contrary to my previous speculation, that it is still possible to sell a million copies of a book. You'll find several examples within this link. (I'd argue, though, that today is still a bit different from the market years ago, and that some of these success stories are uniquely the result of the YA cross-media-promotional phenomenon, as well as authors with outsized platforms for promotion. A pure, original, non-branded author would have a difficult time replicating King's success arc when he was still young in the publishing game. Otherwise, someone like Bentley Little should be selling millions in hardcover...)