For some reason, it never occurs to people that textbook writers can be bad writers. But think about it. Just because a person is very bright in, say, math or English, it doesn't mean that person can explain math or English well.

And people are different. Some textbooks are just plain confusing because one particular writer doesn't explain things in a way that a particular reader can follow.

I know many graduate students who work as tutors in colleges, and they always carry around a tattered, well-worn book they've clung to for years. They do this because that book explains things better than any other.

The point of all this is simple. You could be struggling in a topic because you're trying to follow writing that just doesn't suit you. If you're having trouble in a subject, try visiting a used book store and browsing through some old textbooks. You will be surprised to see how much they differ--and how much one may seem so much more sensible than another.