Ferrari, G. R. F., City and Soul in Plato's Republic, Chicago: University of Chicago Press, 2005.

Excerpt:

In this short book I attempt to say what Plato is getting at in the Republic. That is a grand ambition for a slim volume. My strategy has been to trace one bright thread, the comparison between the structure of a society and that of the individual soul, a theme that runs through the Republic and binds it argument.

Online:
Amazon