There are two libraries I use often and they have English books as well.
The first is the Pestalozzi Library and they even seem to have an english website. http://pbz.ch/info/engl.htm . You will have to pay an annual fee of 45.00.
The other is the Zentralbibliothek. This is really more of a university library but they have a section devoted to books from North America. The only annoying things is that it is a bit hard to browser as the books are arranged by when they aquired them rather than in alphabetical order and they mix non-fiction and fiction together. To get a card is free and that then allows you also to borrow from a number of libraries in other cities or to get books shipped to Zurich (for free) from there. They don't seem to have an english version of their website, but the main one is here: http://www.zb.uzh.ch/ .
ETHZ has libraries as well but I have never used them so I have no idea if you can just get a card for them even if you do not study there.
This website will tell you everything that you need to know and can be used to search which library has which books (it is in English): http://www.nebis.ch/index_e.html
I like reading and studying in the main Pestalozzi library (pestalozzi.ch). It's got wide, long bench-like tables you can sit at, and you can open the windows, too. Lots of people use them for studying. There are lockers, too, so you can go and have a coffee.
Most of the public libraries have place to sit and study/read. I can recommend Zentralbibliothek Zürich, Cantonal Library, Zähringerplatz. 6 / Wallisellen Bibliothek, Zentralstrasse 9, 8304