Broadly speaking, Bitcoin is a scheme designed to facilitate the transfer of value between parties. Unlike traditional payment systems, which transfer funds denominated in sovereign currencies, Bitcoin has its own metric for value called bitcoin (with lowercase letter "b," and abbreviated as BTC1). Bitcoin is a complex scheme, and its implementation involves a combination of cryptography, distributed algorithms, and incentive driven behavior. Moreover, recent developments suggest that Bitcoin operations may involve risks whose nature and proportion are little, if at all, understood. In light of these considerations, the purpose of this book is to provide the necessary technical background to understand basic Bitcoin operations and document a set of empirical regularities related to Bitcoin usage.