sony ereader uses linux os, so there's already a full file system on internal memory and sd card, it should be REAL EASY for sony to use the current interface to display/navigate directory structure, like first show the top level folders, button-> goes down 1 level, until you hit a book, then button-> read
i think this will vastly improve reader's usability
this could be a good hack that's very useful...
unfortunately no source code from sony otherwise i will spend time modifying it