If you're looking to learn theory only and you're not interested in real world stuff, you may ignore my comment. Most probably I will get downvoted for this, there are no good sources for learning RL I tried every course out there including and not limited to:
All of these courses will keep torturing you with cryptic mathematical formulas that unless you're interested in learning the mathematical foundations, are a waste of time to understand. You don't learn how to drive a car by learning how he expanding combustion gases push the piston, both are 2 completely different things. My advice is learn on a need-basis, look for whatever is necessary to solve the problem at hand and learn how it's done (if the problem requires the use of RL) otherwise, wait for Andrew NG to create a DRL course which I'm sure you don't want to miss.