Amazon has announced that its first subscription book service, like Spotify for books, has launched in the US.

The Kindle Unlimited service costs $10 per month and delivers ebooks and audiobooks to subscribers.

In total there are over 600,000 titles to be read. There will also be over 2,000 audio books through the Audible service. Users have unlimited access to those titles.

Amazon's Kindle Unlimited service has been rumoured for several months as a competitor to the likes of Scribd and Oyster.

Kindle Unlimited is available via the Kindle app which can be installed on the Kindle ereader as well as iOS, Android and Windows Phone devices. It will, of course, be on Kindle's own Fire tablets too.

"Finding a great book is easy, and there are never any due dates," Amazon said in its announcement. "Customers can choose from bestsellers like 'The Hunger Games,' 'Diary of a Wimpy Kid,' and 'The Lord of the Rings.'"

The service is US only right now, with a 30 free trial, but will likely launch internationally in due course.

Amazon has its work cut out for itself charing $10 per month when Scribd, which is already well established with a vast 40 million book library, is just $9 per month.

READ: Scribd launches e-book subscription service, unlimited books for $8.99/month