title_body: Editing a published epub book
upvoted_answer: Do you see this as in this picture when you're trying to edit an eBook?
  
  You can only edit EPUB and AZW3 formats!
  
  Here's the tutorial with pictures how to proceed when editing eBook in Calibre.
  
  As an alternative, you can use Sigil to create and/or edit EPUB format.