Though Kindles and Nooks are becoming almost as common as books, more than half of all U.S. readers don't know they can borrow e-books from their local library, a Pew Center poll showed on Friday.

The poll showed 62 percent of readers didn't know if their library had e-books for lending, and only 12 percent of Americans 16 and older who read e-books had borrowed at least one from a library in the past year.

"The most important thing libraries can do is make sure e-books are accessible through the rest of the library system," said Micah May, the director of strategy at the New York Public Library, about raising e-book lending awareness.

Of those who had borrowed e-books, 66 percent said their library's selection was at least "good," while only 4 percent thought theirs was "poor," the survey said.

There are difficulties, occasionally, with the process, with 56 percent of borrowers saying their libraries didn't have a particular e-book while 52 percent found there was a waiting list to borrow a book they wanted. Some 18 percent had incompatible readers for the e-books they wanted.

May said most e-book lending problems were due to the current library e-book distribution system. On Thursday, book publisher Penguin agreed to digitally lend its books to the NYPL, joining Random House and HarperCollins to become only the third of the "Big Six" publishing companies to lend e-books through libraries.

Simon and Schuster, Macmillan and Hachette don't lend new e-books through libraries, according to Publisher's Weekly.

Print readers expressed interest in e-books, though. Of those who don't borrow e-books, 46 percent said they'd be at least somewhat likely to borrow a device pre-loaded with a book, while 32 percent would be at least somewhat interested in learning how to use an e-reader or download e-books.

Those who borrow e-books are much heavier readers than those who don't, averaging six more books than non-borrowers last year.

The lack of knowledge about libraries and e-books means many readers still buy; 55 percent of e-book readers with library cards prefer to buy their e-books, while 46 percent said they prefer purchasing printed books.

The purchasing numbers lessen with those who borrow e-books; 33 percent of e-book borrowers prefer to buy e-books and 57 percent prefer to borrow them.

Reading is still important to many Americans. Fifty-eight percent of those 16 and older have library cards, while 69 percent said the library was important to them.

The Pew poll surveyed 2,986 Americans aged 16 and older by phone with a margin of error of 2 percentage points.