[Ortep]

I think the use of tags would be enough. Just like almost any MP3 player does. Sort on 'album name', 'artist', 'song title' and 'genre'

For books it would be 'series' (For things like trilogies) 'Author', ' book title' and genre.

You don't need directories for that. Only software that is capable of reading the tags and sorting on that. It is standard in mobi type files. But Windows is quite capable of generating tags for any type of file like .doc or .rtf

I guess that linux would be able to do the same

I really don't care were on my Cybook the files are located. I also don't care were the files on my Creative Zen MP3 player are located. I find them by looking for an artist or a genre, not by browsing a directory structure

If that software arranges the files themselves in a treelike directory structure, one master directory or even one big 'database' like Oracle does not matter