Amazon is quietly testing its own subscription e-book service, Kindle Unlimited, according to a report by Laura Hazard Owen at GigaOm. Owen reports finding pages touting the new service, since removed, on the Amazon site offering unlimited access to more than 600,000 e-books for $9.99 a month.

While Amazon has yet to confirm the new service, it has been rumored and expected that Amazon is looking for a way to offer its own subscription e-book service alongside such ventures as Scribd, Oyster, and for children, Epic! and FarFaria.

According to Owen, the service claims to offer more than 600,000 titles, including many titles from Amazon publishing imprints, in addition to some titles from Bloomsbury, Houghton Mifflin Harcourt, W.W. Norton, Workman’s and some other publishers. She reported that, so far, she has not seen any titles offered from Big Five publishers. While S&S and HarperCollins do offer their titles via Oyster and Scribd—HarperCollins also offers its titles via Epic! and FarFaria—the rest of the Big Five have yet to offer their titles through any of the subscription services.

In response to the news of Kindle Unlimited, Scribd co-founder and CEO, Trip Adler said, "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. Publishers, authors and readers alike have all seen the benefit, so it’s no surprise they'd want to test the waters. 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."