It is fascinating. People often disregard the book because its main thesis, the identity of a mole within MI5, appears to be misguided in light of post-Cold War knowledge. But there's more to the book than Wright's speculations -- it's his direct experiences with things like analyzing The Thing that make the book worth reading.
"The Ministry of Ungentlemanly Warfare: Churchill's Mavericks" by Giles Milton describes a lot of the equipment that SOE developed - e.g. the original limpet mine depending on condoms and boiled sweets and, of course, developed in someone's shed and tested at the local swimming pool.
