Oh yeah....it's amazing how true to life he can be!!
You are correct, Series and Series_Index are calibre metadata. But they can be added by anyone. I'm not sure exactly how Kris got the Marvin App to be able to sort with the metadata, but it's pretty awesome. It seems like any app/reader should be able to scan the opf for metadata...they do it all the time for other functions... I guess they just don't feel the need.
