I have half my books on the Aura (1800+ presently). I use the virtual libraries in Calibre to separate Archive, Aura, Sony for those PDFs that don't convert well to epubs (though I find the Sony's low definition difficult to bear now I've tasted the Aura). I also have a virtual Library for an uncle to whom I offered the PRS-T1 Sony (at the time the latest) for his 90th birthday, which I manage.
After much shuffling around, I have now limited myself to 38 shelves:
- one for a very few starred books, limited to one each of authors I discovered very recently (not those I knew and loved before having a reader), whom I want to follow
- one for presently read books and one for those to read in the near future (I try to keep the first category under 12, 24 for the second, to keep it to a max of 2 pages on the Aura
- one each for the less numerous languages
- one for the bought books
- one for complete works
- one each for genre (action, poetry, essays, travel, juvenile etc.), but none for novels
- one each for a few countries (greek, latin, japanese, russian litterature)
- one for short stories (I started it recently, so is incomplete
I don't wish to have too many shelves, and I find the information in the metadata and the calibre catalogs sufficient for the few series I read.