Saturday was a banner day for the J.K. Rowling's Harry Potter series. On Tuesday it was announced that the seventh and final installment in the series, "Harry Potter and the Deathly Hollows," sold 8.3 million copies in the U.S. and 2.65 million copies in the U.K.

Both figures were unprecedented.

Commentary: In a time when it seems like digital media is perceived to be king, it is amazing to think that a book could sell over 10 million copies in the U.S and U.K. alone. That is the equivalent of having a music album go Platinum five times over within 24 hours of its release.

Very impressive indeed.