The book provides a synthesis of the very heterogeneous social network literature. In doing so, it proposes a research methodology for a systematic literature review: Content Analysis in conjunction with Multiple Correspondence Analysis and Cluster Analysis. The need for such a procedure emerges when literature in a particular area is characterized by an internal diversity of approaches and disagreements over the definitions of its fundamental concepts. This is the case of social network studies where such a diversity stimulates a question about the existence of a substantial network theory. The book represents an attempt to answer to such a question. After having investigated the lines of development of social network analysis and provided a sociological explanation of strategic and organizational phenomena in network terms, the work presents a systematic classification of the network effects as recognized by literature and a typology of network studies which identifies 5 different clusters. The results of the study seem to confirm the existence of a substantial, general concept beyond social network studies, the one of social capital.