a new player for my pack World of Dragons is reporting the following issue. it's the very first I've heard of it.

client crash report:
https://pastebin.com/ycDTnGaG

Using guidebook 2.8.3

is this fixed in build 2.9.1?

Huh.... Caused by: java.lang.ClassNotFoundException: gigaherz.common.ItemRegistered
That's in an embedded dependency. A "jar in a jar". It's meant to be extracted automatically by forge, on first use, so it makes no sense for it to not be there. Unless they are using an older version of forge, from before the "new" dependency extraction system... Powered by Forge 14.23.5.2836... which is not the case.
I have no idea why dependency extraction is failing for them, but in any case, it can't be an issue in Guidebook, it's either an issue in forge, the launcher, or the computer/os installation.

FYI: That extraction process seems to be quite unreliable, we're getting reports about it all the time, too.

Seems like something that would need to be fixed in forge, then. I'm phasing out this commons lib in 1.13, but that doesn't mean I won't eventually create something similar again.