A study presented by book marketing firm Verso Advertising at Digital Book World last week finds that 15.8 percent of book buyers already own an e-reader—that figure has doubled since 2010. But 51.8 percent of book buyers say they are “not at all likely” to purchase one in the next 12 months. That is up from 40 percent in 2009. Update: Here’s our follow-up post on why some book buyers are increasingly resistant to e-readers.

SEE ALSO: Why Some Book Buyers Are Increasingly Resistant To E-Readers

Among “avid” book buyers—those who purchase 10 or more books per year—e-reader penetration is more pronounced: 22.3 percent of avid book buyers already own an e-reader, and 10.1 percent say they’re “very likely” to buy one in the next 12 months. But 49.7 percent of avid book buyers say they are not at all likely to purchase one.

Tablet usage shows “accelerated early majority” phasing: 15.2 percent of book buyers own a tablet and 9 percent are “very likely” to buy one in the next 12 months.

Verso predicts an installed base of e-readers and tablets in the 25 to 30 percent range in the next year—with the resistors staying even at about 50 percent of the population.

Verso’s findings dovetail with some research from Bowker/BISG that found e-book growth slower than previously predicted. When Bowker asked e-book power buyers (who buy at least four e-books per month) what is keeping them from buying more, 28 percent said “cost”, 27 percent said “nothing” and 25 percent said they didn’t have enough time. Those factors may affect e-reader resistance, as well. Update: Here are some more reasons.

Verso’s study was conducted between November 30 and December 4, 2011 and had 2,200 respondents. More here.

See all our Digital Book World coverage here.