This book by famed French astronomer Jean Dufay, effectively bridges the gap between the introductory and advanced technical treatment that the subject of astrophysics receives. Originally written in French, this English translation of the authoritative read by O Gingerich makes for a comprehensive guide for all those interested in observational physics.In this book, the author has restricted his discussion to the stars normally seen. Doing so, Dufay then explores the modern-day methods of stellar spectroscopy and photometry. Further, the author has also analysed the prominent results of research work involving the classification and properties of stars. The text also contains some additional topics to increase knowledge in readers such as the construction of Hertzsprung-Russell diagrams, star mass and densities, Yerkes two-dimensional classification, constitution of the stellar atmospheres along with the general theories that surround it and the evolution of stars.While the text is highly informative for the wealth of information it contains, what makes it more useful is the fact that it has been presented by the author is a readable format. in fact, because the text takes a mid-level approach in presenting information, it can be appreciated by not just the professionals in astrophysics, but also by the students of physics.It is useful for several categories of people, including professionals, students, hobbyists with some knowledge of astronomy and specialists seeking to soar up into the world of astrophysics.