Kobo sqlite database
Both the eReader and the desktop software stores it's books and meta information in sqlite databases.
Books that are bought from the Kobo book store are not stored as epub files but are stored in a sqlite database. (on the kobo reader it's under the hidden folder .kobo)
Plus, any epub or pdf's you add to the kobo including any that are stored on an sd-card are loaded into this sqlite database. NOTE: The entire epub/pdf is not stored in the database, but things like title, author, chapters, read status, etc are.
I've started analyzing this database format and plan to write a little program to help manage things like cover images, read status (read, unread, finished), etc.
Is anyone interested in something like this?
Plus if anyone wants, I'll post my documentation on the sqlite database schema.