It is very good to learn more mathematical thinking methods.
But don't look at those commonly used and biased knowledge points. Unless you want to get full marks in the college entrance examination, you can still watch it.
It doesn't matter what books you read, what matters is that you practice often. It is not enough to know how to do it, but also to sum up, that is to say, which chapter of knowledge is examined in the topic. It's been a long time since I graduated, but I know all the books and chapters in high school.
It doesn't matter whether you can buy the book or not. In fact, don't spend too much effort on the surface, but do it in a down-to-earth way. Don't be impatient, impetuous, submit to humiliation and keep a low profile. . .