What is using it like? Command line? Would it be familiar-ish to someone with Unix / DOS experience or totally foreign?
(which coincidentally, is why I want to explore it)
Here's the official IBM "for dummies" book: https://www.redbooks.ibm.com/redbooks/pdfs/sg246366.pdf
Google will show you images of ispf, browsing the jcl manuals will give you nightmares.
I have only had brief contact with JCL, but I remember having to figure out how to get a command line into JCL that was more than 80 characters in length. It took me two days to figure that out, and none of the old-timers in the team had ever had to do that. When I did find the solution, it was surprisingly simple, but finding it took me a lot of time.