This book, in all its revisions, has been in print for more than thirty-five years. It has been found very useful by students and general readers who are already well versed in tonal music systems and want a primer on the basic ideas behind the serial composition methods that grew up and matured during the 20th Century. The book says that it is an introduction to the music of Schoenberg, Berg, and Webern. While most of the musical examples are drawn from their music, examples from other composers such as Bartok, Babbit, Stravinsky, and others are also included.
Perle lays out some of the basic issues of organization that grew out of atonality and how the idea of sets or rows was used to provide order. He shows various kinds of serial organization including sets fewer than twelve tones, hexachords, and the full twelve tone set. He also does a great job in demonstrating the different ways composers implemented this organization principle. It is important to realize that the information here is really just what it says: an introduction. Composers have come up with many other kinds of implementations of the idea of serialization and sets. It is vital to keep in mind that there is no ordained way of composing with twelve tones. There are some basic postulates in the Schoenberg method, but no composer has to be bound by them other than by choosing to compose music that way.
Perle also shows the reader how composers use these rows and combine them in ways that create effects that are not a part of any of the rows including constructions that look like major and minor triads. Yes, your ear will pick them up quite readily, but the way the "move" is not tonal. However, they provide interesting color and a way for the composer to draw the ear to certain aspects of the composition.
There are also many other technical matters of the "standard" method of serialization that are not included here. But who would expect an introduction to be comprehensive?