Understanding the technology that makes cryptocurrencies possible, and an exploration of non-financial use cases for blockchain. This book presents a view of various consensus protocols, reasons for their pro and cons, explains the how and why of each part of a blockchain system, and gives a narrative view of our journey in building a novel blockchain protocol decoupled from cryptocurrencies. The increasing adoption of blockchain for non-financial use cases is currently satisfied by using technologies built with a cryptocurrency embedded in all their logic, with disastrous consequences.