Hi, I just registered here to report a bug
My calibre defaut folder was called "Bibliothèque calibre" (I'm french) and the "è" letter creates a bug with the plugin.
I renamed default calibre folder and it worked, thanks a lot for the plugin
Correcting the bug could be nice for futur users
Calibre: 0.9.2
Plugin: mobi_unpack_v0541_plugin.zip