Amazon.com appears to be testing a new subscription model that would give members all-you-can-read access to more than 600,000 ebooks for $9.99 a month.
Popular books such as "Water for Elephants," "Life of Pi," "Moneyball" and the Harry Potter and Hunger Games series were listed as being part of Kindle Unlimited. The bulk of titles appeared to be from smaller publishers.
One page that Amazon has yet to pull down enables users to search its website and limit results to "KU Test" -- presumably Kindle Unlimited Test. That search function showed 638,532 titles as of 10 a.m. PDT on Wednesday.
The program also appears to include access to thousands of audiobooks.
We've reached out to Seattle-based Amazon for comment, but haven't heard back yet.
Kindle Unlimited would compete with similar offerings from digital libraries Oyster and Scribd. Oyster offers unlimited access to more than 500,000 books for $9.95 a month. Scribd users, meanwhile, can read unlimited books for $8.99 a month.
On Wednesday, Scribd co-founder and Chief Executive Trip Adler acknowledged Amazon's move and said it was "no surprise they'd want to test the waters." But he said Scribd wasn't worried about the Kindle program.
"The apparent entrance of Amazon into [the] subscription market is exciting for the industry as a whole. It's validation that we've built something great here at Scribd," Adler said. "Successful companies don't fear competition, but rather embrace it, learn from it and use it to continue to fuel their own innovation, which is exactly what we [intend] to continue doing."
Oyster's co-founder and CEO, Eric Stromberg, also released a statement saying the company was "not surprised" by Amazon's interest in the subscription ebooks model.
"They have pivoted from transactional to subscription-based in other media, and have had limited success," Stromberg said. "They really paved the way in ebooks, and it's exciting to see them embrace the market we created as the future of books."