Niklas Luhmann's monumental work, The Society of Society (1997), is the culmination of his systems theory and offers a comprehensive theory of modern society as a communication system. The work is divided into five chapters, spread across two volumes. 

1 - Society as a Social System
Luhmann defines society as an operationally closed system of communications. It consists not of people or actions, but solely of communications that relate to one another. The distinction between system and environment enables the observation of society through its own operations. Meaning is the medium that structures social communication.

Through operational closure, society remains autonomous while remaining connected to other systems (e.g., the psyche, organizations) through structural couplings. Topics such as cognition, complexity, world society, and claims to rationality demonstrate how society observes and adapts to its environment.

2 - Communication Media
Luhmann analyzes various communication media. He distinguishes between dissemination media (language, writing, electronic media) and symbolically generalized communication media (money, power, love, truth). Media structure communication by enabling selectivity and stabilizing expectations.

The transition from language to writing, printing, and electronic media changed the form of social self-organization and differentiation. Symbolically generalized media, which are assigned to specific functional systems such as the economy (money), politics (power), and science (truth), are particularly important.

3 - Evolution
Luhmann applies principles of evolutionary theory to society. Evolution occurs through variation, selection, and restabilization. Media play a selective role.

Social evolution is contingent and not goal-oriented. There is no return to previous states (path dependency). Technology, ideas, and subsystems also develop evolutionarily. Memory stabilizes experiences without blocking the openness of future development.

4 - Differentiation
Luhmann explains the transformation from simple to complex social forms. System differentiation is the key to understanding modern societies. He distinguishes between segmental, stratified, and functional differentiation. Modern societies are functionally differentiated, i.e., they consist of autonomous subsystems (e.g., law, economy, politics) that operate according to their own codes.

Topics such as inclusion/exclusion, center/periphery, organization, interaction, and globalization are analyzed using differentiation theory. Social integration does not occur through consensus, but rather through the mutual restriction of the degrees of freedom of subsystems.

5 - Self-Descriptions
Luhmann discusses how society observes and describes itself. Society cannot fully attain itself, therefore self-descriptions arise, often in the form of semantics (e.g., the semantics of Old Europe).

He analyzes various historical semantics: ontology, politics/ethics, school traditions, nations, classes, modernization. Identity paradoxes, mass media, risk, and postmodernity are also treated as forms of social self-observation. Society is described as a paradoxical system that can only observe itself in distinction from itself.

Conclusion
Luhmann's work deconstructs classical social theories and replaces them with a systems-theoretical perspective. Society is not a whole with a center and a periphery; not an aggregate of individuals, but a communication system that organizes, observes, and describes itself.

His contribution lies not in normative statements, but in providing a conceptual framework for understanding the inherent logic of modern society.