Only just done this myself, and I wondered if this is the expected behaviour?
Connect Device (N7) Calibre starts a none intruptable job of scanning for books
Scans the entire device for over 5min and lists many items.
Over 50 entries on a device with NO books.
Even when books are added, it still lists these other files, is this what you intended, or is there a way to limit the scan to a folder on the device?
As it is, it's pretty much unusable for me.
