The main goal of the book is to introduce the reader to the world of spiral galaxies, how spirals were discovered, what they represent from a physical point of view, and what people have learned about the universe and the nature of galaxies in general from the study of spirals. Topics include early discoveries of nebulae, the island universe concept, the structure of spirals as seen both visually with telescopes and in images obtained with different filters, the role of spirals in the discovery of interstellar dust and dark matter, the different kinds of spiral galaxies and the importance of bars and rings, how different non-spiral galaxy types such as elliptical galaxies and S0 galaxies connect to spirals, and how spirals have contributed to our understanding of star formation and evolution, galaxy formation and evolution, the cosmological distance scale, and the universal expansion. The Milky Way as a spiral galaxy is also discussed.
The book is profusely illustrated and not only a discourse on the spirals, but is also a personal reminiscence based on the author's studies of spiral galaxies over the past 45 years.