I actually think a really good idea would be the core devs take a break from actually working on Opal for a week, and to work on documentation instead
@AstonJ amen brother. That said, the things I’ve been working on for Opal are already pretty well documented here 
As for the rest of the stuff, your expertise is as good as mine - I have to poke around the source code to figure out what’s what and ask stupid questions.
Wonder what @adambeynon, @elia, @vais think about this?
What I think about this is that Opal needs help with documentation. If good documentation has not happened so far, there are reasons for it, and these reasons, whatever they may be, are still here, so this situation is not going to change, and no amount of complaining is going to change it. @dancinglightning posted an excellent issue to the opalrb.org issue tracker just the other day titled Getting started considered harmful outlining everything that’s wrong with the site (and with Opal docs by extension). And he’s right.
What can be done is for someone (wink wink) to start this “good documentation” project, let it be wrong, and let @adambeynon, @elia, and @meh correct it. If the skeleton is there, if the bones are good, people will contribute to fleshing it out and correct mistakes. I think GitBook works well - it can be a separate repo, like Volt’s. The first step is to just create a good outline, i.e. what chapters do we need, chapter titles, the flow, etc. Then start fleshing it out and reach out to the Opal core for feedback/corrections.
This is just my personal 2 cents, it is not intended to represent the opinions of Opal project owners who can chime in here as they see fit.
TL;DR
…they can then pass this on to the rest of us to tart up or put into some kind of organised format…
I think you got that exactly backwards.