This book nicely mixes perspectives from economics, organization theory, and strategic management. The writing style is lucid and accessible, unlike many books by academics. It is clear that Dean Roberts has been thinking about these issues for many years.
Even though he was trained as a classical economist, he seems to have shed some of the baggage that the neoclassical paradigm imposes. That is important to the relevance of his ideas in this age of the resource-based view of the firm (see the collected readings edited by Nicolai J. Foss), the importance of entrepreneurship and innovation (Schumpeterian/Austrian economics), and evolutionary economics (An Evolutionary Theory of Economic Change by Richard Nelson and Sid Winter, 1982).
In contrast to the traditional notion that firms within an industry are homogeneous and compete only on price, a stream of empirical research going back to 1991 (Richard P. Rumelt in Strategic Management Journal) has found that rates of return vary more within industries than across them. That makes the case for heterogeneity, not homogeneity. It also speaks to the importance of differentiation among firms. Most important, it opens up the discussion to such vital topics as a firm's unique capabilities, its routines, its culture, and its architecture, all of which Dean Roberts addresses in this remarkable book.
His perspective is not the final one, of course. What we know about that miraculous black box called the firm continues to evolve. But Dean Roberts has made a stunning contribution to what we know. In our own work valuing private equity, we use key precepts of this book every day. I recommend The Modern Firm without hesitation or qualification.