Calibre
From Funiaita
Replacing an existing book
- Open the metadata
 - drag&drop the new book onto the old book (target the right format)
 
Link to book (or other formats like a .zip) on desktop
- Select the book in the library
 - Press 'o' (Open book folder)
 - with the RIGHT mouse button, drag&drop the format you want to your desktop/folder and select "Create shortcut here"
 
For example a .zip with code for the chapters of the book?
- Open the metadata
 - drag&drop the non-book in the area where all the formats are shown