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…