Originally Posted by Doitsu
AFAIK, both the Kobo app and the actual Kobo store all books in a sqlite database, which means that you cannot simply copy or delete a book without using Calibre or a sqlite manager.
That's not correct. Kobo uses the sqlite database for Kobo e-pubs (kepubs) but you can side load and manage any other non-DRM'ed e-pubs with drag and drop via windows explorer. Most (not quite all) books at the Kobo store are available in their proprietary kepub format or a normal Adobe DRM e-pub.