This is great and, in my experience, non-trivial advice. I often used to get stuck on a mathematics textbook, and wouldn't know how to go forward. Turns out, so

This is great and, in my experience, non-trivial advice. I often used to get stuck on a mathematics textbook, and wouldn't know how to go forward. Turns out, sometimes different textbooks covering the same topic will be much better, or even just will be better for teaching one specific concept.