Amazon announced Friday (July 18th) that it's launched an e-book subscription service called "Kindle Unlimited." The service lets Amazon customers pay $9.99 every month for unlimited access to 600 thousand e-books and more than 2,000 audio books. The subscription can be accessed on any Kindle or Kindle app on any mobile device. With the addition of this service Amazon can now compete with similar services such as Scribd, Oyster and Entitle. (TIME)