Welcom
You should spend some time with the FAQ
http://manual.calibre-ebook.com/faq....tory-structure
You have heard about this one.
http://manual.calibre-ebook.com/faq....rked-drive-nas
BTW The Main DB is NOT in a Json file
Also, For those just metadata cases.
checkout Add From ISBN (built into ADD)
And My Fav
Import Book List (a PI)