Publishers Weekly takes a long, interesting look at the question of library e-books and what they mean for both the publishing and library industries. To some librarians’ surprise, library e-books are proving extremely popular with patrons.

"It’s amazing," says Diane Eidelman, administrator for member services at the Suffolk Cooperative Library System, a consortium of over 50 libraries on New York’s Long Island. "We just can’t keep up with the e-book demand. We’ll purchase an enormous amount of content, and within 24 hours it’s all checked out."

Indeed, the numbers tell the story. In the past 18 months, the Suffolk consortium’s e-book expenditures have tripled. In the first few months of 2011 alone, Eidelman says, the library system has increased its e-book budget by 66%. And still, patrons can’t get e-books fast enough. Earlier this month, the e-book version of James Patterson’s 2010 thriller, Don’t Blink, had a staggering 108 holds, she says, even though the library tries to purchase enough copies so there are no more than two reserves at a time. "We’ll probably have to buy more copies," she notes. "We believe that’s good customer service. But it is incredibly expensive. E-book purchases really are almost patron-driven at this point, and every few months we put more money into e-books."

Library e-book provider Overdrive reports that library e-book usage is essentially doubling every year, and some publishers are getting concerned. Apart from the widely-reported HarperCollins decision to impose lending limits, Simon & Schuster and Macmillan don’t lend library e-books at all.

"We have not yet found a business model that makes us happy," S&S CEO Carolyn Reidy explains in a recent Publishing Point interview. Macmillan CEO John Sargent, in another Publishing Point interview, suggests that free digital copies that can be delivered conveniently right to one’s device was at issue. "It’s like Netflix, but you don’t pay for it. How is that a good model for us?" Sargent asks.

But others, such as a vice president of Random House, point out that libraries “create readers” and getting library readers hooked on their books is not a bad thing, free or not.

Still, given that it is not really possible for a library to “own” an e-book in the same sense as it owns its paper books—or for that matter, to transfer ownership to other libraries or send it out via interlibrary loan—the question of what is going to happen to libraries as e-books wax and paper books wane is a thorny one that has a number of industry professionals concerned. Is a library without any physical books at all still a library?

Someday, we may find out.