Personally, I think Sun Tzu's Art of War is a set of practical theoretical system, which can be used for reference by future generations and can be used flexibly in sudden wars. Reading is like fighting. Make good use of the art of war, there must be a good strategy. If all the reference materials are used wrongly, the war will naturally fail. Soldiers are more expensive than dragons. Everything we do is to pursue a better result and make it develop in a good direction, but we don't want it to develop in a bad direction. So I think if I go to school, I still support reading textbooks carefully and doing more questions. Some people write sloppy reference materials through various means for economic benefits. It is meaningless for us to refer to them at this time, which may lead you to deviate from the correct learning ideas. For example, you know what Phoenix is by watching TV, but you have never seen it with your own eyes. Is it true or not? You can't study it yourself. Therefore, by reading the textbook, even if everyone has everyone's understanding, it will not be influenced by other people's established concepts, so that your understanding of the problem and its essence will be more thorough, which is called original insight.