The book provides a critical synthesis of studies in sociolinguistic covariation, accessible to readers with basic linguistic knowledge, and serves as both an introductory resource and a standard reference in the field. It balances readability with theoretical and methodological depth, discussing important sociolinguistic concepts and issues such as language variation and categoricity through practical examples. Although commendable, it leaves some topics like markedness and ancient perspectives on variation underexplored, while its teaching approach might benefit from additional resources for learners.