Amazon.com on Friday launched an e-book and audiobook subscription service, “Kindle Unlimited,” that could make it the Netflix of e-books.

The largest online retailer in the world introduced Kindle Unlimited, offering “unlimited access” to over 600,000 titles — including “Life of Pi,” “The Hunger Games” and “Harry Potter” series — and thousands of audiobooks on any device for $9.99 a month, and a month’s free trial. Amazon AMZN, -1.78% already has a “Kindle Owners Lending Library,” which permits Amazon Prime members to borrow one book a month (membership costs $99 a year).

“Right now I would say Amazon is the biggest and best bet to become the Netflix of e-books,” says technology consultant Jeff Kagan. Amazon has a ready-made library of titles, and the infrastructure in place after two decades in the online retail industry, he says, but it can’t afford to get left behind as consumers move from downloading to streaming and renting. “The business model of the industry is changing. That creates enormous growth opportunities for current leaders in the e-book space — namely Amazon.com,” Kagan adds.

Publishing experts say more companies are finding ways to allow readers to swap e-books, read them for a monthly subscription, or rent them from an e-library. Kindle owners who are also Amazon Prime members can already choose from over 300,000 books to borrow for free with no due dates, but they may only choose one book a month. Services such as eBookFling.com and Lendle.me give Kindle and Barnes and Noble’s Nook customers access to tens of thousands of other potential e-book lenders for a 14-day period.

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So far, however, there is no book-streaming or rental service with the scope and selection of Spotify for music, or Netflix for movies and television. “I’m skeptical that the economics of e-book subscriptions will be compelling enough for authors published by the big corporate houses to play along,” says Simon Lipskar, the president of Writers House, a literary agency in New York. “Subscriptions are fabulous models for the branded platform, fabulous for the heavy-use consumer — and usually quite wretched for the creators of the works.”

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But consumers want the same flexibility they have with music and movies. “We’re increasingly addicted to instant gratification,” says Evan Carroll, digital media analyst and co-author of “Your Digital Afterlife.” That, he says, is why people stream music with Spotify and Pandora, and movies through Netflix and Hulu. “I anticipate that we will see more e-book publishers take this approach in the near future,” he says. Peter Hildick-Smith, president of book market researcher Codex Group, agrees. “It’s the next logical step in the market’s evolution,” he says.

There is a burgeoning market in e-book rentals. Safari Books Online — which has a website and apps on iOS and Android — has partnered with over 100 publishers to provide access to technology e-books on a subscription model; it has over 30,000 IT e-books. “Think of it as Netflix streaming for professional developers,” says Safari’s director of marketing Troy Petersen. Texas Southern University and California State rent text e-books at discounts of up to 60% off the print price through CourseSmart.com, a digital service that began in 2007 and partners with 100 universities and colleges.

Startup Oyster Books charges $9.95 a month for unlimited reading, and offers more than 500,000 titles from over 1,600 publishers. “Oyster’s challenge will be to prove that they can make the model profitable for Oyster,” says Mark Coker, founder of e-book distributor Smashwords.com. Rival Scribd offers unlimited books for rent for $8.99, with 300,000 books from more than 900 publishers. Entitle offers two e-books a month for $9.99, including new releases and best sellers, such as “Hard Choices” by Hillary Clinton and “Mr. Mercedes” by Stephen King.

It will be an uphill battle to get mainstream publishers and authors onboard, experts say. A successful e-book rental or subscription service will need to convince publishers that the service augments — rather than replaces — traditional e-book retailer sales, Coker says. It may make more sense to rent books, however, considering people tend to read them just once: “A song is a three- to four-minute customer experience, which is often repeated with the same song multiple times,” he says. “A book is a multi-hour experience, but is seldom read a second or third time.”

If e-book rentals take off, they may only make financial sense for avid readers. “Paying $9.95 a month for the premium Spotify is probably more than I used to spend on purchasing songs or albums,” says Neil Schlager, founder of Schlager Group, a publisher of materials for students and teachers, “but I’m happy to do it because the service has value to me.” But e-books prices are still low compared with print copies, Coker says. Amazon charges $9.99 for new and best-selling e-books. “Any e-book subscription or rental service needs to meet or beat what retailers are already doing,” he says.

(This story has been updated.)