title_body: How to effectively manage ebooks using Calibre?
upvoted_answer: As written in the Calibre manual you should use tags:
  
  
    But suppose you want to find all unread science fiction books. There’s no easy way to do this with this folder scheme, [...] In calibre, you would instead use tags to mark genre and read status and then just use a simple search query like tag:scifi and not tag:read.
  
  
  It might take a while to get everything properly tagged, but after that it will be easy to find what you want.