Intellectual property rights are a key element in today's knowledge economy. Specifically, the use of patents as transactional elements has become widespread. However, the market for patents possesses specific features that differentiate it from other markets. This book provides evidence for its existence and addresses its particular conditions. It also takes a deep dive into patent intermediaries, discussing how they emerged, their activity and business models, as well as their impact on market structure, firms, and societies. Patent intermediaries participate in market transactions by offering various services and by bridging supply and demand of patents. In the last decades, some of them (so-called pejoratively 'patent trolls') have become popular for their aggressive litigiousness. However, the activity and presence of patent intermediaries are much more significant. To enhance our understanding of the role of patent intermediaries, the authors provide a comprehensive review of the role of these agents in the Economy.