My reasoning is "I don't know what I don't know" on the first pass and my first goal is to understand that all of the things "exist", then how things individually work.
Another trick I've learned is to find an older copy of a specification and read that first. Usually the older copies have less bulk, are more directly addressing the core conceptual issues, and are easier to read.
Sometimes if I want a rapid and superficial understanding I just go after the diffs or change notes for the last few versions of whatever it is. This can give a scattershot coverage of the contemporary state of the thing. It's not much but it's a place to start from.
In defense of the other people here - often doing this properly involves a bit of a dense pre-read to make sure you can at least understand where these might be applicable. With a totally new area to you there's a big learning curve there.