Amazon is planning to start an unlimited e-book subscription for $9.99 a month that will give limitless access to over 600,000 titles.

Amazon, the online retail powerhouse, is testing a new e-book deal for its customers that will give them unlimited access to a wide range of digital content. Kindle Unlimited is Amazon's new e-book and audiobook subscription model that offers unbound access to over 600,000 titles and thousands of audiobooks for just $9.99 per month, according to a Google cached test page. The service will be available on all devices, including Android and Apple iOS tablets and iPhones.

The apparent test site was viewable online for a brief time and was taken down Wednesday. Some Kindle Boards users had already spotted Amazon's new subscription model, which quickly became a hot topic of discussion for e-book readers. According to GigaOm, which originally reported the news, popular book titles such as "Water for Elephants," "Life of Pi," "Hunger Games" and the "Harry Potter" series were a part of the unlimited subscription model. Book categories included science fiction, romance, and mystery/thriller and suspense.

Amazon's Kindle Unlimited subscription, if made available, will not be an entirely new option. Rivals' subscription services such as Scribd and Oyster already offer similar models. Scribd's monthly subscription for unlimited reads costs $8.99 per month. But the addition of an unlimited subscription will be popular among avid readers on the world's largest online retailer's network. The suggested subscription price may be slightly higher than the competitor but Amazon compensates by offering an extensive choice of content for its readers.

"This could be a huge game changer in the publishing field, changing the economic model of the entire industry," Dan Olds, The Gabriel Consulting Group analyst, told Computer World. "There are going to be some sticky problems, like how to work out compensation between the myriad of large and small publishers, plus those who publish for themselves using Amazon as their sole distribution platform. But I think this could be wildly popular with readers."

GigaOm also posted a promotional video for Kindle Unlimited on YouTube, which sheds more light on the new model along with a free 30 days trial when the service is launched.