Before giving this book a five-star rating, I tried to find fault with it. I could not. It is just what I need.
Clearly and precisely, with plenty of illustrations from Ordnance Survey maps, the book teaches the skills of navigating with a map and compass, including more advanced techniques such as aiming off and using back bearings, and then shows how a GPS can be used to make navigation more effective, whether or not you have a mapping receiver. If you do have one, a chapter on mapping software shows how your GPS can communicate with your computer. Finally, it teaches you how to get out of trouble -- even if your batteries go flat or the Americans switch the satellites off.
The book is small and light enough to fit into a rucksack and has a plastic cover which should help to protect it from the elements. It also comes with a bonus: a transparent plastic "navigation aid" on which is a compass rose, a couple of romer scales, and a list of things to do if your GPS fails .