Not true in the slightest. Many chapters in textbooks used post-secondary education institutes are either regurgitating things you already knew from pre-req cla

Not true in the slightest. Many chapters in textbooks used post-secondary education institutes are either regurgitating things you already knew from pre-req classes or things you don't need (i.e. not part of the course curriculum). While in theory you're right, in practice I find that I rarely use more than half of any textbook in a single given class (less, if multiple textbooks are assigned).