Gavin Mortimer’s World War II in Secret: The Hidden Conflict 1939 to 1945, introduces the casual reader to the many fascinating “secret” aspects of World War II, from top secret weapons programs and technologies to espionage, resistance movements, and covert and clandestine missions.

Typical television fare such as German V-weapons, Enigma, the Doolittle Raid, Italian human torpedoes, and the Manhattan Project are included, of course, but so are more obscure technologies, missions, and secrets.

This makes for an entertaining read, with a surprising amount of information about the more intriguing and obscure “secret” subjects of World War II packed into one attractive package. One of the best features of this book is that the content is broad in scope, and so subjects such as Great Britain’s network of guerrilla Auxiliary Units, meant to fight on if the Germans invaded; the Comet escape line that got more than 800 Allied soldiers and aircrew out of Occupied Europe; the Warsaw Ghetto fighters; the roots of the French Resistance; and Australia’s Z Special Unit get some well-deserved attention.

The book is handsomely laid out and well illustrated with photos, diagrams, and drawings, although there are a few inexplicable errors. A drawing purporting to show the location of Barnes Wallis’ bouncing bomb in an Avro Lancaster bomber instead highlights the retracted mainwheel of a Vickers Wellington. An image in a story about German jet fighters captioned as a Gloster Meteor is technically a Meteor, but the aircraft pictured is actually the world’s first turboprop aircraft, the Trent Meteor. In addition, the photo is reversed.

But these are small errors unlikely to greatly trouble the audience for whom the book is intended. More of an introduction to secret aspects of World War II than a comprehensive history, World War II in Secret: The Hidden Conflict 1939 to 1945 is an engaging book that casts a wide net for interesting subject matter while also providing unexpected depth.