Just had a quick skim over some of that chapter, and it is very compelling, especially when I see how well its worked for AwesomeWM (my desktop environment of choice) and how many commercial games are using it for user scripting [1].
I think the most compelling thing about Lua (to someone with no Lua experience), is that its appears (from examples, and what people have said) that its good for embedding inside another program (size wise and good FFI).
In a video I saw, by one of the designers of the languages stated that this was the original purpose (engineers using this instead of C, with the low level details done by programming team in C).
Java having lots of jobs isnt a good metric, because theres lots of jobs also means theres lots of people applying, in fact I would say a good reason to not use Java would be to simply weed away (some) people applying
It might be my relative newness to software, but I enjoy looking at other peoples code to see what works (pick up new language features) and what doesnt.
[1] http://en.wikipedia.org/wiki/Category:Lua-scripted_video_gam...