The book focuses on the design, testing and manufacture of the F-1 engine, but also covers its incorporation into the first stage of the Saturn V and in-flight record. It concludes with an examination of what might have been, if the F-1 had not been discarded, together with the Saturn V, at the conclusion of the Apollo program. The account draws on original documents and interviews with engineers and managers, and is illustrated by many never-before-published photographs, both colour and monochrome. The intention is for this to be the definitive account of the development of this most powerful of rocket engines. As NASA is developing an evolved version of the hydrogen-burning J-2 engine for use in the forthcoming Ares launch vehicles, the author includes development of the J-2 engine within the context of the Saturn V development, thus bringing rocket engine development up to the present and thus provide this book with a long shelf life.