'The Second Textbook' is a nice perspective which resonates with me. In my experience I've found the need for as many textbooks as I can get my paws on - each book usually handles one or other topic better than others, or gives me that extra angle that helps my understanding.
Yeah, and there is path dependence in learning, too! The Feynman lectures are quite deep and insightful, but because of that probably good to circle back to at different times, as an example.
But the real kicker for me was just breaking through the impression that “understanding” is a function of rereading, getting stuck, and focusing on one explanation as if parsing the syntax of some author’s statement was how you got information and understanding of a subject. My general rule now is to simply read different explanations. That, imo, is how you develop pedagogical awareness, too, as you then begin to see what authors are not saying in their attempt to convey a subject.
