Here's a place to find / add further information related to the above book. Scroll down to see a list of the Routes from the book, click on the one you are interested in.
The book gives a series of walks through the New Territories, each accompanied by a map, lots of photos, and further information. You can approach it as a hiking guide-book - each route takes you through an interesting part of Hong Kong's countryside. But if you'd like to see some of the remains of Hong Kong's wartime history you'll find them especially interesting.