Painstaking analysis of the 1994 civil war in the central African nation of Rwanda, in which hundreds of thousands of civilians were slaughtered. Genocide seems a species of unforeseeable madness, writes the author, a French social scientist. It is not: It is ``a historical product, not a biological fatality or a `spontaneous' bestial outburst.'' In the case of Rwanda, the extreme enmity between the Tutsi and Hutu is the result of a long history of Belgian, German, and French colonialism that played on and amplified existing ethnic tensions, tensions exacerbated by one of the highest population densities in the world and what the author deems ``an almost monstrous degree of social control,'' loosened and ultimately undone by rural unrest. When that social control dissolved, the final ``historical product'' was the deaths of at least 800,000 people and the displacement of another two million--and all this out of a total population of seven million. Prunier offers a heavily documented account of the Rwandan civil war, one that allows the nonspecialist to follow the complex waves of history that washed over that unfortunate nation only a year ago. He also stresses the urgent question of how this horror could have occurred in our time. Considering modern theories of violence and ethnic strife, Prunier concludes that the genocide served as a vehicle for self-identification: to preserve ``a certain vision [the Tutsi and Hutu] have of themselves, of the others and of their place in the world.'' It also occurred, he says, because of blind obedience, fear, self-interest, and overpopulation. The last will emerge ever more prominently in future wars, Prunier predicts. ``Genocides are a modern phenomenon--they require organisation--and they are likely to become more frequent.'' If genocides are indeed the wave of the future, this may become a primary textbook for understanding why.