"DOUBLE DECKER C666" is the second book in a trilogy written by the author that I much enjoyed. Haupt-Heydemarck describes in exciting - and at times, harrowing - detail many of the missions he flew as an observer with his pilot "Take" Engmann on long-range reconnaissance and bombing missions against the French in the Champagne Region during 1916. Each chapter has illustrations depicting various aspects of the life Haupt-Heydemarck experienced as a frontline aviator, as well as photos taken by Haupt-Heydemarck himself, which give the war a real world immediacy. Especially touching is the close relationship he had formed with Engmann, which made them an efficient combat team. This book is priceless.