This book identifies the relevant determinants of modern software markets, and incorporates these in a simulation model that provides the basis for an integrated theory of software markets. The novel approach overcomes the deficiencies of existing approaches such as Network Effect Theory or Models of Network Diffusion, which do not sufficiently explain the phenomena of modern software markets. Here, the focus is on software for data manipulation, storage, and/or transmission in the corporate world. Based on a study of the largest 1000 German and US companies, the author presents a comparative analysis of the market for enterprise resource planning systems, Electronic Data Interchange (EDI) solutions, and office communication applications. By integrating empirical, theoretical and simulation results von Westarp provides buyers and sellers of software products with valuable and insightful managerial advice.