Still unsure about the potential of digital book publishing, or, more specifically, the trajectory of the e-reader market? Sales of portable devices such as Amazon’s Kindle and Barnes & Noble’s Nook that are used solely for the purpose of downloading and reading e-books are outpacing the more interactive, Web-enabled tablet computers such as Apple’s iPad and the Samsung Galaxy Tab. Twelve percent of adults in the U.S. owned an e-reader as of May 2011, twice the amount recorded by the same Pew Internet research project in November 2010. Eight percent of American adults owned tablets in May 2011, up from 5 percent in November 2010. There is, however, some overlap among ownership of the two devices. Three percent of U.S. adults own both an e-reader and a tablet, while 9 percent own an e-book reader but not a tablet, and 5 percent own a tablet computer but not an e-reader.