The Pew Research Center's Internet & American Life Project has released The Rise of E-reading.
Here's an excerpt:
One-fifth of American adults (21%) report that they have read an e-book in the past year, and this number increased following a gift-giving season that saw a spike in the ownership of both tablet computers and e-book reading devices such as the original Kindles and Nooks. In mid-December 2011, 17% of American adults had reported they read an e-book in the previous year; by February, 2012, the share increased to 21%.
| Institutional Repository and ETD Bibliography 2011 | Digital Scholarship |