Thanks.
In the guide I see "Reports of other similarly easy installations for other operating systems, to be included here, are especially welcome." So here is a log of what I did on my Mac.
I installed jing using brew. (Long install with brew, and quite a bit of chatter, but it seems to be working.)
The instructions in the guide could be improved to make it clear what role aota.xml has in this command:
jing /path/to/pretext.rng aota.xml.
I first tried using my highest level ptx file. Doing that gave me several
error: element "xi:include" not allowed anywhere;
So I'm assuming this doesn't follow includes. If I run it on one of the lowest level ptx files, then I get a report that seems to flag various improper things, mostly of the form
element "some element" not allowed here.
So I probably have a bunch of things to fix. I see jing works with multiple files, so to do the entire book, I can use
jing /path/to/pretext.rng src/*.ptx