Even as e-book sales surge, Americans are slow to look to their public libraries to take advantage of the format, a study showed Friday.

The Pew Internet & American Life Project found just 12 percent of Americans ages 16 and older who read e-books say they have borrowed an e-book from a library in the past year.

The study found most Americans are not aware they can borrow e-books from libraries, even though three-quarters of US public libraries offer the service.

Some 62 percent of those surveyed said did not know if their library offered e-book lending. Just 22 percent said they knew their library lends out e-books, and 14 percent said their library does not lend electronic books.

Even among tablet computer owners, 53 percent said they were unaware of their local library's e-book efforts.

Top bookseller Amazon last year said it was selling more digital than print books, but even owners of the Amazon Kindle were not looking to their library, the survey found.

"It was a genuine surprise to see these data, especially after all of the attention that has been paid to the tension between libraries and major book publishers about whether many of the most popular books should be available for lending by libraries," said Lee Rainie, director of the Pew Internet Project.

"E-book borrowing is gaining a foothold in the library world and will likely grow much more in the future as more people become aware of it."

But the survey also found those who wanted to borrow e-books faced problems: 56 percent of e-book borrowers said that at one point they had tried to borrow a particular book and found that the library did not carry it.

And 52 percent of the group found a waiting list to borrow the book they wanted.