Artificial Intelligence: A Modern Approach
Russell and Norvig organised the field around one idea, the rational agent that acts so as to maximise its expected outcome.
Why it matters
Scattered approaches acquired a common frame, and AI is still taught from this book.
The agent frame let search, logic, probability, learning and perception be presented as answers to one question rather than as separate traditions. The book shifted the emphasis noticeably from symbolic reasoning toward probability and learning before that shift had happened in the research itself. It has run through several editions and is translated into dozens of languages.