If it was so short, why you just skimmed through it?

You are seeing a few parts (titles, maybe a paragraph or two, a sample of the diagrams and pictures) and you are not seeing the system behind it. You have to read it whole to properly understand its point.

And as that system is not isolated from the world, after you understanding it you will get a good hint of the outer system, things that are happening in the real world outside of it.