Aiken is a functional programming language designed for writing smart contracts on Cardano . Named after physicist and computing pioneer Howard Aiken, it is written in Rust, released under an open-source license, and built specifically for the Cardano blockchain. Aiken provides a smooth developer experience and features state-of-the-art tooling, drawing inspiration from modern languages like Rust, Elm and Gleam. This book begins by exploring the history of smart contracts before focusing on Cardano's 'first principles' approach, which is grounded in academic research. It delves into the differentiators and design decisions behind the Extended Unspent Transaction Output (eUTxO) model, helping readers appreciate the paradigm shift required for writing smart contracts with Aiken on Cardano. Aiken's GA (General Available) Release was September 2024 and the language has seen rapid adoption since, now responsible for the vast majority of Cardano transactions. Structured into 66 bite-sized chunks, this book takes you from 'zero to hero' and guides you on your next steps with Aiken 'I am a simple man and I want simple answers' - Howard Aiken 'Aiken is incredible really. Plutus on rocket fuel' - John Woods, Algorand CTO 'We're starting to fall in love with Aiken a little bit' - Charles Hoskinson, co-founder Cardano