Verdict: Of the four agentic AI books worth your time in 2026, Antonio Gulli's Agentic Design Patterns wins for most builders. It is the most pattern-complete of the set, it works as a desk reference rather than a one-pass read, and the author made the full pre-print PDF and per-chapter notebooks publicly available, so the effective cost of entry is nothing. Micheal Lanham's AI Agents in Action, Second Edition is the runner-up and the better buy if you want the current production stack in o...