Amazon officially launches Kindle Unlimited, ebook and audiobook subscription service for $9.99/month

Amazon(s AMZN) has officially launched Kindle Unlimited, the $9.99/month ebook and audiobook subscription service we told you about on Wednesday.

The details are, pretty much, what already leaked. The service is only available in the U.S. for now. About 640,000 titles are available, most from Amazon’s own publishing imprints or by self-published authors who’d previously enrolled their books in KDP Select. There are books from traditional publishers as well — no big-5 publishers — but Abrams, Algonquin, Workman, Open Road and Bloomsbury, among others. Two thousand audiobooks from Audible are included, and a membership to Kindle Unlimited comes with a free three-month Audible subscription.

“You can keep up to ten books at a time and there are no due dates,” according to Amazon’s help pages. “Read your Kindle Unlimited books on any Kindle device or free Kindle reading apps.”

One splashy series of note that is available: The first three books in the bestselling eight-book series Diary of a Wimpy Kid, published by Abrams. Here are some details on how Amazon is paying authors whose books are included in Kindle Unlimited: Publishers like Abrams don’t have to actively participate for Amazon to include their books; it may simply be paying Abrams each time someone reads a Wimpy Kid book through the service. (We’ve asked Abrams for comment.)

There’s a 30-day free trial.

“With Kindle Unlimited, you won’t have to think twice before you try a new author or genre—you can just start reading and listening,” Russ Grandinetti, SVP of Kindle, said in a statement. said Russ Grandinetti, Senior Vice President, Kindle. “In addition to offering over 600,000 ebooks, Kindle Unlimited is also by far the most cost-effective way to enjoy audiobooks and eBooks together. With thousands of Whispersync for Voice-enabled audiobooks to choose from, you can easily switch between reading and listening to a book, allowing the story to continue even when your eyes are busy.”

More to come once I’ve parsed some of the details.