It was really only a matter of time.

Amazon briefly put up and then removed a page on its website for an unlimited e-book and audiobook subscription service called Kindle Unlimited, as first reported by Gigaom.

A signup page for the service was spotted by multiple users on Twitter on Wednesday. According to a cache of that page (see below), Amazon plans to offer users unlimited access to 600,000 digital books for $9.99 a month.

Reps for Amazon did not immediately respond to our request for comment.

Kindle Unlimited. $9.99 subscription for over 600K books. When will this go live? http://t.co/3sHUyrSjzc pic.twitter.com/dDZMC84g4o — DearAuthor (@dearauthor) July 16, 2014

The e-book subscription space took off in late 2013 when startups Oyster and Scribd launched unlimited Netflix-style subscription services for e-books. Both Oyster and Scribd reached partnerships with a number of publishers, including two of the big five publishing houses.

Trip Adler, CEO and cofounder of Scribd, framed Amazon's possible entry into e-book subscriptions as being a "validation" of its own efforts in a statement provided to Mashable. Likewise, Oyster CEO Eric Stromberg suggested it would be a positive for the e-book space as a whole.

"We’re not surprised. They have pivoted from transactional to subscription-based in other media, and have had limited success," Stromberg said in a statement. "They really paved the way in ebooks, and it’s exciting to see them embrace the market we created as the future of books.”

Amazon's pricing is comparable to Oyster and Scribd, which charge $9.95 a month and $8.99 a month, respectively. Of course, Amazon has the advantage of a much larger existing customer base.

A list of available titles for the Kindle Unlimited subscription was still online as of publication. The list includes titles like The Hunger Games, 1984, Flash Boys and The 7 Habits of Highly Effective People.