Originally Posted by theducks
I think the extension was chosen so it would NOT be associated with any other program. In essence, it is a BAK file and I know of no other program that opens BAK files.
no - in essence it is a properly formatted EPUB - its not a backup format
, it is just a renamed file - that is why rename, then Open with sigil works fine.
but FYI, programs that open proper "backup format" files include Word, Excel...