I'll have to try that explaining tip.

In the past, all the stuff I've learned has been either easy, or an extension of things that I was already interested in and experienced with. Reading Model Theory was the first time in my life where I read a chapter of a textbook and it made absolutely no sense. In fact, it took about three passes per chapter before they made sense.

Ah! I hate that. From context it sounds like you learn similarly to me.

I'm not sure if I'm being naïve (for never having needed to do this before) ...

I think you are, but in a good way. I've encountered similar things on the occasions - thinking about it - when I had to actually learn things from my highschool math course rather than simply going "ah, yes, this." So my current theory is poor presentation. (Other theories being tiredness - I was tired a lot at the time - or simply not being that great at math, personally, just liable to read a lot.)