There are 192 states in the world and counting. Over the last two centuries, this number has swelled, contracted, and swelled again -- the last two bursts having been intimately connected with the collapse of Soviet power. Inspired by what has happened in eastern Europe and the former Soviet Union, Roeder reopens the venerable topic of where nation-states come from, of which succeed and which fail. He has a fresh answer that challenges traditional explanations, such as the rise of nationalism or the enabling effect of international sanction. Instead, he maintains in a wonderfully well-argued and broadly researched book, the key is a subunit that has its own political identity, boundaries, and institutions, not ethnic cohesion alone, grievances, or dreams of nationhood. Roeder's label for the subunit -- whether a colony or a federal subject -- is "segmented state." Its institutions and the politics that it permits internally and with the central state not only precede nationalism but also give force to it. Roeder is at his best when explaining why there is, say, a newly independent Turkmenistan and not a sovereign Turkestan and when and why the national projects of segmented states lead to national crisis.