title_body: How do I open my Ebook library in kindle?
upvoted_answer: In Calibre, the Add books menu choice has several options. One is:
  
  "Add books from directories, including sub-directories (Multiple books per directory, assumes every ebook file is a different book): Allows you to choose a directory. The directory and all its sub-directories are scanned recursively and any ebooks found are added to the library. calibre assumes that each directory contains many books. All ebook files with the same name in a directory are assumed to be the same book in different formats. Ebooks with different names are added as different books."
  
  If you point to the folder and use that Add option, it will do them all,see this: