The Association of American Publishers reported that eBook sales were up 202% and overtook paper book sales in February 2011.
So, I wasn’t surprised to read Amazon’s announcement that Kindle ebook sales overtook paper book sales there around the same time frame (March).
Amazon reported that since April 1, they have sold 105 Kindle ebooks for every 100 paper books. Amazon also notes that the new advertisement supported $114 WiF-only Kindle reader is the best selling Kindle device. They have sold three times as many Kindle readers in the first quarter of 2011 than in the same quarter of 2010.