After two and a half years of living in Geneva, I have discovered the wonderful municipal library. http://www.ville-ge.ch/bm/fr/bibliotheque/bm_cite.php
Tucked away just behind the cinema Pathé Rex, a tall glass building with a very nice atmosphere.
Not only can you get books there (in French, English, German, Italian, Spanish, Portuguese), but you can also rent DVDs, or music, audiobooks, language learning packages, tourist guides, ...
Or you can use the library as an elevator to the old town. Wonderful place, and the membership and rental (except for movies) is free.
You can rent up to 20 items at a time, and for a month. Items can be prolonged over internet.
I'm sorry I didn't go there earlier.