Amory Lovins is a justifiably renowned physicist and environmentalist who promotes energy-use and energy-production ideas based on conservation, efficiency, use of renewable energy-sources, and generating energy near where it is actually used as opposed to huge centralized capital-intensive megaprojects like nuclear power plants. He may be best known for being co-founder and chief scientist of the Rocky Mountain Institute or being credited with his work on the design on an ultra-efficient automobile, the Hypercar.
Soft Energy Paths is about ideas which have become much more familiar since its publication back in 1977 — critiques of the "hard energy path" he describes as involving inefficient liquid-fuel automotive transport and centralized electricity generating facilities, often burning fossil fuels or using nuclear fission, technologies that waste huge amounts of energy and are enormously capital-intensive, along with advocacy of "soft energy technologies " such as solar, wind, biofuels, geothermal, etc.
This book may be considered outdated (published in 1977) and some of its predictions seem quaint (he talks about oil prices rising to $30 a barrel) but, having read this book, I believe that Lovins' ideas are fundamental to a general understanding and conceptual overview of why we need to move away from capital-intensive, ultra-high-tech energy solutions toward sustainable technologies and conservation measures. These ideas have now become widely popular, but for the serious student of energy policy, this book is a good source of very detailed thinking and extensive footnotes.
The book is absolutely jam-packed with informational tidbits such as the following example quoted from page 41: "The fifth type of economy available to small systems arises from mass production. Consider...the 100-odd million cars in the U.S. In round numbers, each car probably has an average cost of less than $4,000 and a shaft power of 100 kilowatts (134 horsepower).