Smith creates a whole typology about ethnic groups. He claims that all ethnic groups (or, as he calls them, 'ethnies', from the French for 'ethnic community') have several key aspects, including a name, common myth of descent, shared history and culture, territory and a sense of solidarity. They also fit into two main categories: lateral ethnies, which are based on an aristocracy and clerisy and rule over an indefinite but often large area, and the vertical ethnies, based on a urban, priestly or artisan class which rule over a small but clearly marked area.

Smith discusses the development of nations in the context of the French Revolution, when the modern concept of citizenship entered the picture, and here his narrative lets up a bit. Devoting most of the book to ethnicity, when he comes to discussing the two main types of modern nations - territorial (or non-ethnic) and ethnic - he spends too much time on the latter and not enough on former. This is an important flaw, since he thereby almost dismisses those nations like the U.S. which do not have an ethnic foundation and thus do not fit his theory.

Nonetheless this book is useful for the sole but important purpose of reinforcing the link between many nations and their ethnic pasts.