Reinforcement Learning: An Introduction, Richard S. Sutton and Andrew G. Barto, 2018 (The MIT Press) - A foundational textbook covering value function approximation, including linear methods and the theoretical underpinnings.
Human-level control through deep reinforcement learning, Volodymyr Mnih, Koray Kavukcuoglu, David Silver, Alex Graves, Ioannis Antonoglou, Daan Wierstra, and Martin Riedmiller, 2015Nature, Vol. 518DOI: 10.1038/nature14236 - A seminal paper demonstrating deep neural networks for approximating Q-values, enabling high-performance control in complex environments.