The service that a few Amazon users spotted making a premature appearance a couple of days ago is today official: Amazon's Kindle Unlimited is a $9.99 subscription that provides access to over 600,000 ebooks and "thousands" of Audible audiobooks. While Amazon touts the Harry Potter and Lord of the Rings series among the titles carrying its new "Read for Free" button for Kindle Unlimited subscribers, this service falls short of giving access to its complete library of content. Amazon sweetens the deal by throwing in a complimentary three-month Audible membership, which expands the audiobook selection to the full range. So Kindle Unlimited has some definite limits on what you can consume, if not how much. You can start a free 30-day trial right away and see if it provides enough incentive to keep it going over the long term.