The book "Geographic Variation of Cratogeomys castanops in the State of Coaguila, Mexico" by Rollin Harold Baker and Robert J. Russell is a study of geographic variation in Cratogeomys castanops in Mexico. The authors consider in detail various aspects of the populations of this species of rodents, paying attention to their evolutionary and biological heredity. The book contains a significant amount of data and results of observations that help to better understand the characteristics of these animals in accordance with the environment where they live. The publication is an important source of information for scientists interested in the geography and ecology of Mexican fauna.