This book offers a lot of modeling but very little understanding. The authors' basic argument is simple; some public goods are cheaper when provided on a large scale, which makes big states more efficient; on the other hand citizen preferences are more heterogeneous in larger states - they can be more easily reconciled in smaller ones. The authors posit that there is an optimal size somewhere between the extremes, determined by this efficiency / cohesion tradeoff. As a speculative hypothesis this even provides a fairly interesting framework for the historical discussion of state size in Europe in chapter 11.

However, historical analyses are unfortunately overshadowed by mathematical modeling in all the other chapters. The authors believe that the tradeoff can be used to 'explain' various aspects of state size. They derive a large set of mathematical equations which supposedly describe their relationships formally. However, the simplifications and assumptions behind the equations are extremely unrealistic, and consequently the derivations become vacuous formal exercises which yield absolutely no information of interest. I can't believe that professional academics waste their time, and fill their books, with such utterly pointless work.

Of course models are idealizations and they can be informative even if they don't correspond exactly to reality, as the authors note in defence of their method. But come on, sociology and history have limits where further abstraction becomes counterproductive. The authors probably crossed these limits so long ago, and are now so far beyond them, that they no longer remember where they lie. The benefits and drawbacks of small and large states are interesting topics for a historical discussion, and maybe a philosophical one as well. But it is simply not a good subject for mathematical analysis. That much quickly becomes clear to readers of this book, if not to its authors.