Based on interviews conducted earlier this month, the study released Thursday shows 50 percent of respondents saying they have a tablet or stand-alone device such as Amazon.com's Kindle. That's up from 43 percent in September.
The survey says nearly 3 out of 10 adults read an e-book over the past year, compared to 23 percent who had done so when asked in 2012. Only around 4 percent read e-books exclusively.
Sales for e-books are growing, but have leveled off over the past couple of years. They're believed to comprise 25 to 30 percent of the general trade market, with commercial fiction especially popular for e-books.