'Beginners will discover a simple and holistic view of the energy conversion and conservation process with an exergy concept. The concise but practical description of the fundamental energy conversion process in various systems, from jet engines and nuclear reactors to the human body, is given. Readers can find useful examples of practical energy conversion processes and systems that use naturally occurring energy resources such as fossil fuels, solar energy, wind power, geothermal power, and nuclear fuel. The chapter 'Exergy in Biological Systems' is an outstanding feature of this textbook. Readers can find fundamental examples with solutions of biomass energy conversion system, such as, 'Animal and Human Systems', 'Nonequilibrium Thermodynamics of Biological Systems', and 'Entropy Production and Exergy Destruction in Humans.'' Yoshiharu Amano, Waseda University