I want to learn everything there is to know about general relativity.

My only issue is I’m not sure of the prerequisite maths that are needed to gain a throrough understanding of the the theory.

As for the courses I’ve taken, I’ve completed all the elementary maths, as well as courses in vector calculus, ODE’s, and PDE’s.

What textbooks can you folks recommend for the next leg? I suspect I obviously need to understand tensor calculus and differential geometry, but I’m at loss of where to go. Thanks.