What would be also interesting is to store all book files in a database. Then you add tags with author, year and so on and then you can create several FUSE file

What would be also interesting is to store all book files in a database. Then you add tags with author, year and so on and then you can create several FUSE filesystem like author/year/title or just author/title or author/series/title. So you can browse you collection in different ways. The same would work for images or music. Genre/artist/album/title or year/artist/album