I wish to learn Gherkin so I can use it with specflow; I am looking for a document I can read on the train e.g. print out on paper.
All I can find on the web is short disconnected descriptions that don’t tell a story and require lots of clicking between web pages to read.
(I don't mind buying a good if it has lots of good Gherkin content in it)
The RSpec book is a great book to introduce some of the concepts of BDD, Rspec(as a .net dev you should check out MSpec) and Cucumber which is a based on Gherkin.
The best free printable resource is the awesome cuke4ninja which has a PRINTABLE pdf (follow instructions in README.md on github to create).
There is a BNF definition https://github.com/aslakhellesoy/gherkin/wiki/BNF if you are that way inclined.
There's a Cucumber book out now too
EDIT: It looks cuke4ninja.com isn't what it was anymore (it's now some dating site) but the site is still kept on github. The link above has been changed.