Absolute Essentials of Ethereum is a concise textbook which guides the reader through the fascinating world of the emerging Ethereum ecosystem, from the basics of how its blockchain works to cutting-edge applications. Written by an experienced educator, each chapter is designed to progress potential students from class to class. Technical concepts are clearly explained for those new to the topic and readers are supported with definitions and summaries in each chapter. Real-life case studies situate the overviews in a contemporary context. Topics covered include the Ethereum Execution and Consensus layers, Ethereum governance and community, Decentralised Autonomous Organisations (DAOs), Decentralised Finance (DeFi), Non-Fungible Tokens (NFTs) and Layer 2. This book is the ideal text to support undergraduate and postgraduate courses on blockchain technologies, cryptocurrencies, Web3 and fintech, as well as for those who want to know how Ethereum really works.