All you have to do is contact Amazon within seven days and
request a refund. Amazon will refund your money and automatically delete the
book from your Kindle account. Below are the steps:
1. Go to Manage Your
Content and Devices.
2.
From
the Your Content tab, select the Actions [...] button
next to the title you want to return, and then select Return for Refund.
3. In the pop-up window, select Return for Refund.
Tip: You can cancel a Kindle book
order from your Fire or Kindle immediately after purchase. Choose
"Purchased by Accident? Cancel this Order" immediately after you
purchase a book on your device.
Bonus: if you are interested in decrypting Kindle books, you can read this post about how to convert Kindle books to any format as you like.
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