A Walking Guide to York's City Walls by Simon Mattam
"...just the right size to take with you as you walk round the walls..."
"A good read which has continued after the city."
"Good book to plan a visit to York. "
If you are in the USA, buy from Amazon.com here
If you are in Europe you can also buy from your local Amazon website by searching for the ISBN above.
Take a look at the article in York's Evening Press.