Between the success of Spotify and Netflix, the flat-fee online subscription service has already taken over music, movies, and TV. Now, Scribd will try to add books to that list. But can it really upset a business where books are already free at the library?

Scribd, the online document-sharing site, struck a deal with HarperCollins publishing yesterday to sell their backlisted books on a subscription service for a monthly fee. That will make older books available for sale, though none of HarperCollins more recent bestsellers will be included in those made available. Consider it a paid digital library card, then, but only in the section in the back of the room.

The price will be about $9 a month, which puts it right near Spotify's $10 and Netflix's $8 fees. That's intentional, of course, as the Scribd CEO Trip Adler pointed to those companies as the clear inspirations for the deal: "Given the success of Netflix in video and Spotify in music, it's inevitable that you're going to have a similar service in the book space--and it could be a really big business," he said to Fast Company. The service looks pretty smooth, too, as TechCrunch's embedded 2001 Neil Gaiman book American Gods shows.

The potential problem with a book subscription service is the same that has affected music and video; the amount that authors and the publishers get paid with the deal. Spotify has taken some criticism recently from artists like Radiohead's Thom Yorke because, in his words, "New artists get paid f–k all with this model." For now, new artists won't suffer from Scribd's plans — remember, only HarperCollins' older books are on the service — but they could soon be channeling Yorke's complaint.

Plus, unlike music and video, books are already free at the local library. And despite financial cutbacks, a recent Pew study found that library use is only increasing. Certainly, e-books have taken off with the rise of tablets and Kindles. But Scribd will need more modern and other publishers to join on board and successfully break into the subscription model business.