The sociology of law is the study of everything about the law that is not its actual text. Let me explain: when most people think of law, they think of the written down rules that government makes, courts decide, and police and regulatory agencies enforce. One way of looking at law is that it is a set of rules that courts and police impose on people. This is not completely how sociologists understand it, though. What sociologists of law do is to take a broader picture of the social and political processes that surround the relationship between law and society. Some questions they have asked is: what is the function of law in society? How do laws get made and who do they benefit? Under what conditions do people obey law and when and why do they evade it? When people in social movements litigate, does it help their cause? Why do people decide to litigate and when do they resolve their conflicts in other ways? What is the role of lawyers in shaping the trajectory of disputes? What do people think law is? How does the understanding people have about law shape how they understand their rights, the actions they can take, and what their relationships to other people are?
Weber, Durkheim, and Parsons (major sociologists) were all interested in understanding the relationship between law and society. Though the soc of law is a subfield of sociology, it is more foundational to the works of major theorists than many mainstream sociologists seem to recognize.
If you want to get an overview of this field, three textbooks may be helpful: *Connecting Law and Society* by Robert L. Kidder, *Law, Order, and Power* by William J. Chambliss and Robert Seidman, and *The Sociology of Law: An Introduction* by Roger Cotterrell. Also, some major articles are contained in a reader edited by Richard L. Abel called *The Law and Society Reader*. If you have access to a university library, you should check out the journals *Law and Society Review* and *Annual Review of Law and Social Science*.
Other notable sociologists of law include Marc Galanter, Lauren Edelman, Robert C. Ellickson, Stewart Macaulay, Susan Silbey, Patricia Ewick, Austin Sarat, Kim Lane Scheppele, and Philip Selznick. This is an abbreviated list and is by no means comprehensive, but it should get you started.