Some of my book covers have disappeared. They were there at one time. If I view the list of books on my Kindle Fire and the cover is blank, I can click on it, it will come up then show up in the carousel, but not on the list. Most of my books were added with calibre and I reformat them to either Mobi or Epub. I'm not too savy of all the editing of Metadata so I may be leaving out a step. Some of the books are public domain, some were DRM free, some were given to me by others.