A pedagogical text that teaches fundamental principles of programming by treating programs as collections of abstractions and interpreters: it emphasizes recursion, higher-order procedures, and data abstraction, uses a small functional language to build and analyze interpreters and compilers, and develops metalinguistic techniques to design new languages; through worked examples it connects modularity, state and objects, streams and concurrency, and performance and implementation details to show how to think systematically about program structure and design.