Originally Posted by johnwhelan
Separate issue is deleting them on the device since Mantano seems to copy them in to a separate directory no doubt it will become clearer over time and that isn't a Calibre issue.(snip)
I hate saying 'me too' again, but that is the case. If you see my post above where Kovid asked me to test deleting books in Calibre, my experience was that Calibre deleted the book in the Calibre library on my Nexus 7, but not in Mantano.
Kovid gave me the explanation about Mantano's 'private library' which Calibre cannot affect.
If I seem to be getting low on space I will uninstall Mantano and swap over to Moon+. However, as I have paid for Mantano, and like it as a reader, I am not anxious to make that change...