As an interpretive guide, this brief volume is no substitute for the Republic itself. It is not even a comprehensive commentary. I analyze many of Plato's arguments in some detail and provide periodic summaries in which I gather them up to show their place in the overarching plan of the Republic, but since I only allude to other arguments, you do yourself a grave disservice if you do not read the original text. Even to get a basic understanding of the interpretive arguments offered here you will need to be familiar with Plato's exposition.
More important, if you do not read the Republic, you deprive yourself of the means for keeping me honest. One way to approach this book is as a particular case study in the art of interpretation; it is an interpretation that I offer here, not the only one possible. I am more interested in your learning generally how interpretations are put together and how one goes about making a case for them than I am in convincing you of my particular interpretation of the Republic.