By the 1530s, the writings of Erasmus accounted for 10 to 20 percent of all book sales in Europe.

Needed to brush up on my Erasmus and so resorted to Wikipedia. Some interesting information:

Erasmus wrote both on ecclesiastic subjects and those of general human interest. By the 1530s, the writings of Erasmus accounted for 10 to 20 percent of all book sales in Europe. He is credited with coining the adage, "In the land of the blind, the one-eyed man is king." With the collaboration of Publio Fausto Andrelini, he formed a Paremiography (collection) of Latin proverbs and adages, commonly titled Adagia. Erasmus is also generally credited with originating the phrase "Pandora's box", arising through an error in his translation of Hesiod's Pandora in which he confused pithos (storage jar) with pyxis (box).

Wow - 10-20% of all book sales. I know the absolute sales were still low in such early days of the printed book, but still. That is an incredibly dominant literary/intellectual/theological position for one person to hold, particularly given that the Bible probably accounted for 50% or more of all book sales at that time.