As mentioned elsewhere I think they do themselves a disservice by starting there, instead of starting with a reasonable set of delimiters etc., and then referring to an aside that explains how to bootstrap to that point. The lowest levels get too esoteric for most.

It's a bit like being taught functional programming by starting with composing everything from combinators, including church numerals for numbers. Sure, knowing those bits is worthwhile theory, but not until you're convinced about the higher level utility.