Not so much a book, but a catalogue of books.

My Bro-in-Law gave me a catalogue today from a Sheffield company He's dealt with who either keep in stock or can supply pretty much any current English language railway related publication available by mail order. Unfortunately they don't appear to have a website yet, but can be contacted on 0114 2558000 (+44-114-255-8000 from overseas). UK address is Mail Order Department, Platform 5 Publishing Ltd, 52 Broadfield Road, Sheffield S8 0XJ England. Neither of us has any connection with this Company, but Bro-in-Law tells me that the guy who runs it is very helpful and knowledgeable.
Keith.