In this richly researched book, Alice Rio explores a period during which the notion of unfreedom has long puzzled historians. Roman slavery has, of course, attracted reams of scholarship; serfdom after the twelfth century continues to provoke seemingly endless debate. The intervening period has often been marginalised, or seen as transitional. This, then, is an extremely important book, reinstating the complexity and subtlety of the ways in which unfreedom worked. In many ways, Rio paints a fairly classic picture of degrees of unfreedom—incidentally, this does raise the question of terminology which could have been more fully addressed in the book. Unfreedom is clearly not a synonym for slavery, and, in many respects, the book appears to be about the former, despite its title. But the book also introduces substantially new material—both conceptually and empirically. The sense of flexibility in degrees of unfreedom is eloquently conveyed, and the functions and origins of this flexibility are carefully considered.