Compiled from posts on expats-in-zurich yahoo group. Thought it might also be helpful here. Please add if you have any ideas.
Where to buy and donate second-hand english books in Zurich
If you want somewhere to donate your books, or pick up some
bargains, here are my favourites!
Caritas Kunst & Krempel, Birmensdorferstrasse 53, 8004 Zurich
http://rcs.caritas.ch/files/zh/Second_Hand_Laeden.pdf
Small charity shop, two shelves of english books at back of shop, but quick turnover. 3CHF each book. Tram 9 or 14 or train to Bahnhof Wiedikon, cross over road, shop is in the middle of the row of shops
Buecher Brocky, Bederstrasse 4 (entrance via Gutenbergstasse.)
http://www.buecher-brocky.ch/
HUGE second hand bookshop, with whole aisle of Eglish books, prices between 1CHF and 4CHF per book. Tram 6 to Bahnhof Enge or 13 to Enge/Bederstrasse. Head towards the Post Office and you'll see the Buecker Brocky signs.
The Pestalozzi Library (several branches in zurich but particularly the Raemistrasse branch) have a good selection of English books & DVDs
http://www.pbz.ch/index.htm
There is an annual membership of either 30 (2 items) or 45chf (25 items) or you can just borrow for a month for 10chf. Take ID with you. They also have occassional booksales
[Added: 17/12] - The Pestalozzi library is actually on Zähringerstrasse 17, sorry! always get those two streets mixed up! Here's the link
http://www.pbz.ch/biblio/hs.htm - there is an annual fee for borrowing, i think it's about 40, or about 25 if you can prove you're a student :-)
The ZentralBibliothek
http://www.zb.unizh.ch/ is the combined Zurich and University library. I've never found 'english novels' there, but then again I've never consciously looked (i'm usually looking for journals and academic texts!) There's no cost to join. it's got a nice cafeteria and lots of working spaces, plus helpful staff
Another place for english books is the main Zurich Brockenhaus
http://www.zuercher-brockenhaus.ch/ behind the HB (Neugasse 11). Go to the Second Floor, and there's a whole self of english books. It's more expensive here than the Bruecker Brocky, but it's got newer/better quality books.
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Or you can join
bookcrossing.com and release books, track books, trade books, send books through the post.....
I buy many of my books through ebay.co.uk. The postage is a lot better than ebay.com esp. since Royal Mail has option for printed-material - either with airmail or surface mail.
For hardbacks, the Amazon.co.uk market place can be worth it since it's the same price for postage regardless of book.
ricardo.ch often has people selling off their books as well.
This isn't second-hand, but I always check exlibris.ch, weltbild,ch and play.com (free international shipping) for books.
Happy Reading.