If you're seeing issues with the covers of your books, there may be a few explanations for the behavior.
Does the issue occur on multiple books from multiple sources? If not, it's possible that you have an incorrectly formatted book. The best thing to do in this situation would be to navigate back to your ebook retailer and redownload the book from the fulfillment link. If that doesn't work, we recommend asking your ebook retailer for a new fulfillment link. Download the book again and see if this corrects your issue.