In 1824, Sadi Carnot postulated a monumental theory, which ranks with the greatest of scientific classics. He became immortal when he published his technical paper "Reflections on the Motive Power of Heat," which included his famous "Carnot cycle" theory. His theory is included in almost every thermodynamics, engineering, and physics course in colleges worldwide. It defines the maximum thermal efficiency of all heat engines operating within the same temperature range. Now, "The Most Efficient Engine" cycle, using a different approach, defines the maximum thermal efficiency as does the Carnot cycle. In addition, it relates temperature, efficiency, and power in a meaningful way, giving better insight to heat engine operation. This book includes the Carnot cycle, the Stirling cycle, and the "Most Efficient Engine" cycle, along with some relevant thermodynamics. As an interesting, surprising, and amazing sidelight, the "Most Efficient Engine" cycle equation, for efficiency at maximum power, is validated by and validates the widely quoted Chambadal - Novikov - Curzon - Ahlborn equation, giving the exact same results. e = 1-SQR (TL/TH) The book will appeal to a broad spectrum of readers. It promises to be another classic