Both Amazon and Barnes & Noble have downplayed actual e-reader device sales numbers, instead crowing about the number of e-books sold in the past year. This is an important distinction because it shows us a few things about the Nook/Kindle audience. First, e-readers (dedicated e-readers, mind you, not tablets) are popular with heavy readers and, as a corollary, most e-reader owners buy a lot of books. However, the real value has been in the e-book format itself, as the popularity of the