I've been making slow but steady progress on the campaign, editing sections and jotting down text for future sections of the Choose Your Own Adventure book version. I also photobashee a couple of bits of artwork for it.
Watching people read old Fighting Fantasy games has helped me identify some of what I want and don't want in the experience of reading the one I'm trying to plan:
It'll need lots of artwork - people love the weird old fantasy art, and though I probably can't swing anything quite so unhinged, my line art photobashes are fairly close in style.
I want to avoid dice rolling or other random chance stuff like lookup tables. It's tempting to include given the source but they break the flow too much and people start skipping them if the bad result is just failure with no forward path. The most I'll include is an inventory.
Every choice needs to go somewhere interesting, even if that means fewer total branches. I don't like the "one true path" school of design where you just end up backtracking. Every branch should be valid and have different content in it so it's worth rereading. So far, the hard part is choosing what stuff goes in what branch, since I already have an open world with plenty of content to divide up.
I also drafted a background for the campaign version. Working on foreground now.