I've been learning representation theory (among other topics) from his Youtube lectures! They're a real treasure trove. And he's got a dry sense of humor that I quite like.

I can also recommend this interview with him by Curt Jaimungal, which is filled with his insights and opinions about his practice of mathematics, and his life as a mathematician: https://youtu.be/xu15ZbxxnUQ

His math lectures have renewed my love of the subject that I had lost in poorly taught undergraduate classes.