You can skip chapters you already understand. I don't know what textbooks you are reading, but almost every single one I have read tried very hard to present t

You can skip chapters you already understand. I don't know what textbooks you are reading, but almost every single one I have read tried very hard to present the content in a matter which focuses on understanding, unlike papers which focus on pure information. I am afraid if you find either cryptic you have a serious lack in the prerequisite knowledge and that is what you need to focus on if you want to understand the subject. From first hand experience I can tell you that I have passed exams on a lot of things I have very little knowledge of right now. Textbooks are essentially the only way to reliable self study academic materials.