Good practices for skipping chapters when reading Assuming I am reading a textbook/paper or any kind of rich material and then there is a point where I feel that the chapter I am reading is unnecessary or insignificant (I can get back to it later if I am wrong) or at times unmotivated or boring, what are good practices to skip such chapters? 

(Assume Math/Engineering books)

How do you make sure that the content you skipped doesn't get in the way of the subsequent chapters? (i.e. Skipping does not carry any drawbacks)
I'm usually backtracking, i.e., I try to read a subsequent chapter, then I usually discover that there are some definitions/concepts that I do not understand, so I go backwards to look these up, and, once I've understood these notions I can resume the reading of the subsequent chapter.