RL courses and books

Reinforcement Learning: An Introduction (Sutton, Barto)

Nearly everybody in RL recommends it. Looks like a book with a well-balanced
depth and readability. Has exercises.
Book link
Github with solutions

Bertsekas course and books

Books may not be in free access. Some of them are dedicated to optimal control
and dynamic programming, which are, strictly speaking, not RL, but close enough.
Course link

Yandex practical RL

Yandex Data Analysis School course, with lectures and assignments on GitHub.
Decent theoretical explanation with the assignments focused on practical needs.
Course GitHub link

Levin deep RL course

Course on deep reinforcement learning, with assignments (text and GitHub).
Rather deep dive into the theory.
Course link (Fall 2021)

David Silver lectures

Well-known lectures on classical RL.
Course link