Reinforcement Learning: An Introduction, Richard S. Sutton and Andrew G. Barto, 2018 (MIT Press) - This is the definitive textbook for reinforcement learning, providing a comprehensive and detailed explanation of dynamic programming, including policy iteration, its theoretical foundations, and practical implementation.
UCL Course on Reinforcement Learning - Lecture 3: Dynamic Programming, David Silver, 2015University College London (UCL) (Google DeepMind) - This lecture provides a clear and accessible explanation of dynamic programming algorithms, including policy iteration, in the context of reinforcement learning.
Markov Decision Processes: Discrete Stochastic Dynamic Programming, Martin L. Puterman, 1994 (John Wiley & Sons) - This book offers a rigorous mathematical treatment of Markov Decision Processes, including a thorough discussion of policy iteration as a fundamental algorithm for solving MDPs.