The number of people in the U.S. who own an e-reader such as Amazon's Kindle or Barnes & Noble's Nook has doubled in the past six months, according to a Pew Internet Life study released Monday, while multi-purpose tablets like the iPad are leveling off. The survey was conducted among 2,277 adults ages 18 and over, 12% of which said they owned an e-reader, up from 6% last November, while tablet ownership went from 5% to 8% in the same period.

The report claims tablets got a boost in the summer and fall of 2010 leading into the holiday season, while e-reader adoption has likely picked up as manufacturers compete fiercely with low-cost devices: the Kindle cost $139 ($114 for the ad-supported edition), the touchscreen Nook costs $139 and Kobo's new touchscreen e-reader comes in at $129.

Correlations between e-reader and tablets are interesting; I've always considered that the two are not direct competitors, as even though tablets also feature digital bookstores they are not equally fit for reading purposes. Not surprisingly the survey found some overlap in ownership between the two types of devices: 3% own both an e-reader and a tablet.

While tablets and e-readers devices are certainly gaining popularity, both are still low on the list of tech gadget ownership. According to Pew, some 83% of respondents said they owned a cell phone (though no breakdown between smartphones and feature phones was offered), 57% own a desktop computer and 56% own a notebook. Meanwhile, 52% of surveyed adults said they own a DVR in their household, and 44% said they had an MP3 player.