It is definitely not a mass storage device when plugged in. There are two locations for book storage -- memory and SmartMedia card. I don't have mine with me, and I'm at the wrong laptop. If no one answers, I'll do the calibre-debug later tonight.
Someone has made
a utility to put books on the device for linux here. I find that it is sometimes buggy when adding a number of books in a row.
m a r
m a r