I created their own category called "finished" and just delete them off the Kindle but not the cloud. I also have one named "delete" for all the trash books, usually free or discounted, that I would delete but don't want to be bothered. Also if you delete a book off your Amazon account, which is a total pain to do, it will let you buy it again, if it's not deleted instead of "buy now" it says something like "open book". I tend to be forgetful so that's helpful.