Book about the series

For Xmas I had a book called, "The Complete Secret Army" by Andy Priestner (ISBN 9780956100009). It is an unofficial guide to the series and the spin off series, "Kessler". Although it is probably more of a reference book, I found it surprisingly easy to read from cover to cover. Goes into the series and everything to do with it. I would definitely recommend it to fans of the tv series. My copy came off Amazon.