Spotify did it for music. Netflix did it for movies. And now, Trip Adler and Scribd are doing it for books.

The 29-year-old entrepreneur and his six-year-old San Francisco startup just unveiled an online subscription service that gives you unlimited access to a large library of digital books for a flat monthly fee, including titles from big-name publishing house HarperCollins.

This isn't a place where you purchase your very own digital copy of Agatha Christie's Murder on the Orient Express. It's a place where you can browse and skim and read whatever strikes your fancy, which might end up as a few paragraphs of the Christie classic sandwiched in between a chapter of Elmore Leonard crime fiction and a cover-to-cover romp through your favorite Neil Gaiman novel.

>'This works so well in video and music. It's inevitable that there's something to do here in the book space too' Trip Adler

Just as Spotify and Netflix used all-you-can-stream services to help carve out a viable online future for music and videos, Adler and company hope to find a subscription sweet-spot for e-books that satisfies online readers as well as publishers. The idea is that this will not only generate revenue for publishers, but give readers broader access to online books – and encourage them to buy titles from other sources.

"This works so well in video and music," Adler says, during a recent visit to WIRED's offices. "It's inevitable that there's something to do here in the book space too."

Scribd isn't the first outfit to offer this sort of e-book subscription service. Just last month, a New York startup called Oyster unleashed an iPhone app that gives you unlimited access to over 100,000 titles for a flat fee, and you get something similar from another service called eReatah. But Scribd is spreading the idea across myriad devices, from iPhones to iPads and Androids phones and Amazon Kindle tablets and any other machine with a web browser, hoping to provide reading material wherever you are.

"That's what you want," says Roger Kay, an analyst with research outfit Endpoint Technologies. "Even though mobility is all the rage, it's good to have the full range."

Trip Adler was at Harvard alongside Facebook founder Mark Zuckerberg – "I was in the class they made The Social Network about," he says – and soon after he graduated, he and another Harvard student, Jared Friedman, launched Scribd. In the beginning, the site was mainly a way for anyone to quickly and easily publish documents to the net, from research papers to legal docs to, well, just about anything else. But it evolved into a tool that let publishers and authors not only get articles and books in front of readers, but also collect money for these digital texts.

Scribd has long offered subscriptions to the rather eclectic array of stuff that winds up on the site, which spans about 40 million books and documents from 100 different countries, written in 80 different languages. And then, this past January, after inking deals with various publishing houses, it started offering subscribers access to a broader range of e-books – though this was never publicized. Now, the company is officially opening its ebook service to the world, giving you unlimited access to its library for $8.99 a month – and injecting titles from HarperCollins.

The service evolved gradually over the past year and change, as Adler tracked the success of Spotify and Netflix in the subscription game and traded notes with old friend Emmet Shear, the founder of video broadcaster Justin.tv, which has also embraced subscriptions. When Adler originally took the idea to HarperCollins, the book publisher wasn't too keen on it. But, together with longtime Scribd advisor Richard Sarnoff, Adler and company developed an economic model that satisfied all parties.

Basically, a publisher gets paid only if a reader chooses one of its particular books – and it only gets paid in full if the book is read in full. "We actually determine whether the book is read and make payments to the publisher based on that," Adler says.

According Jan Johnson of Red Wheel Weiser Books, one of the publishers providing books for the service, the setup makes sense for her book house not only economically, but because it gives people a way of discovering books they might buy elsewhere. The service makes particular sense, she says, because it taps the already large number of people that use Scribd, many of whom are already paying a subscription fee. Scribd now claims 80 million active users.

"Scribd can convert these people over to the book subscriptions," Johnson says. "We are all for this, and we think it will just expand our audience. People will either read a book there, on the service, or buy the book in some other way if they want to keep it in their own library – either their electronic library or their real library. Some people still read books on paper."

>'People will either read a book there, on the service, or buy the book in some other way if they want to keep it in their own library – either their electronic library or their real library' Jan Johnson

The question is whether the model satisfies the authors too. This is hardly a steady stream of income for a group of artists that has so few ways of making money, but they too can benefit from the way the service introduces readers new titles – at least in theory. "It's good for authors if it succeeds in a widening an audience." says Greg Sterling, an analyst with Opus Research. "It almost works best as a marketing vehicle as opposed to a revenue generator."

This seems to be the way the book world is moving. Oyster declines to say exactly how it shares revenues from its subscription services, but it will say that it "pays authors when their books are read."

On the other side of things, you have to ask how big the appetite is for an e-book subscription service among the world's internet users. Pretty much everyone listens to music and watches movies, but the number of people who spend a good chunk of their time with books is smaller – to say the least – and Scribd faces big competition in the digital book game from the likes of Amazon and Google and Apple.

None of these tech giants offers a subscription service at the moment, but Amazon does offer a book-lending service – which is somewhat similar – and if any of these companies get into subscriptions, they have an added leverage that Scribd doesn't.

And yet each of the three is likely to push its particular service on certain devices over others. Amazon is most interested in Kindle, Google in Android, Apple in iOS devices. Scribd plays across all that hardware – even synchronizing how many pages you've read – and like Oyster, it has the advantage of being there first.

"We expect this to change reading behavior significantly. It makes it so much easier to browse, to sample books, to read books in parallel, to search for information within books," Adler says. "That's different from what Amazon does."