If you are going to Switzerland, and you want a good railway bookshop, I can recommend Sinwel in Bern (http://www.sinwel.ch/kontakt.php
) - which I found by chance. Like most specialist bookshops, a bit pricey, but I was less concerned about the price than availability. If you visit, make sure you ask at the counter about secondhand books. When I did so, they got out a key, took me down into the basement, and let me into a storage room full of second hand railway books.
You can easily walk it from the main station.