IMO textbooks are dead and they were never a great source of knowledge to begin with. The idea of reading some piece of text written by someone, then edited by someone else, and expressed in an "appropriate" style and language (think formal language which uses fancy jargon), and then having to robotically solve some end-of-chapter problems is just absurd. My experience tells me the "gems" of knowledge are often found when authors and experts just say whatever the fuck they want on a forum or in personal discussions. That obviously presumes those authors actually know what they're talking about. So many math, physics, engineering, etc. books are written by people who had no business talking about those topics.