This book is a text book written for classroom education. It's very thorough and is written for an HVAC Service Mechanic. The version I received was a little old, but refrigeration was invented in the 1880's and not much has changed in the basics department. Sure refrigerants are different and you have to recover the gas these days ... but a motor is the same, and so are compressors, expansion valves, and for a few bucks, this book will explain a lot.