Reinforcement Learning: An Introduction, Richard S. Sutton and Andrew G. Barto, 2018 (The MIT Press) - The textbook on reinforcement learning, providing foundational concepts on tabular methods, the challenges of large state spaces, and the introduction to function approximation.
Dynamic Programming and Optimal Control, Vol. II: Approximate Dynamic Programming, Dimitri P. Bertsekas, 2012 (Athena Scientific) - A comprehensive resource that details approximate dynamic programming methods, offering a theoretical foundation for using function approximation in large-scale control and reinforcement learning problems, particularly those with continuous state spaces.