Reinforcement Learning: An Introduction, Richard S. Sutton and Andrew G. Barto, 2018 (MIT Press) - This foundational textbook comprehensively defines and discusses episodic and continuing tasks, their differing return definitions (undiscounted vs. discounted), and their implications for RL algorithms.
Reinforcement Learning Course, David Silver, 2015 - Lecture 2, 'Markov Decision Processes,' from this prominent university course clearly explains the distinction between episodic and continuing tasks and the role of the discount factor, providing an excellent academic perspective.
Deep Reinforcement Learning: An Overview, Yuxi Li, 2018IEEE Signal Processing Magazine, Vol. 35 (IEEE)DOI: 10.1109/MSP.2018.2796322 - This survey article, while focused on deep RL, includes a clear introduction to the fundamentals of reinforcement learning, including the distinction between episodic and continuing tasks and the definition of different return types.