Amazon Kindle readers are beginning to receive credits in their accounts, as part of an e-book antitrust settlement.
In 2013, a federal court approved legal settlements by Hachette, HarperCollins, Simon & Schuster, Macmillan, and Penguin which stemmed from alleged e-book price fixing on Kindle books purchased between April 1, 2010 and May 21, 2012. Amazon has more details about how the credits work:
Eligible customers do not need to do anything to receive these credits. If you are eligible, we have already calculated your credit and added it to your Amazon account. As long as you have credit remaining we will automatically apply it to your next purchase of a Kindle book or a print book sold by Amazon.com, regardless of publisher. The credit applied to your purchase will appear in your order summary. Eligible customers should have received a notification email from Amazon on July 23, 2015.