Hello! I was looking for a library to implement the guide, I stopped at your mod.
I added to build.gradle of my mod:

repositories {
    maven {
        url 'http://dogforce-games.com/maven'
    }
}
dependencies {
    deobfCompile "gigaherz.guidebook:Guidebook-1.12.2:2.6.0"
}

added handler:

@Optional.Method(modid="gbook")
@SubscribeEvent
public static void registerBook(BookRegistryEvent event) {
    event.register(ModResources.getResource("xml/guide.xml"));
}

added dependencies = "after:gbook" to main mod class. I do not think that I was wrong somewhere here.
Build mod and launch client... and crash:
https://gist.github.com/KorDum/7406297fb58ac7eff74fc856e51fcee1

Need some more core mod?

Do you need any more information?

Hello, I think you have to add also another of my libraries:

deobfCompile "gigaherz.commons:gigaherz.commons-1.12.1:0.6.4"

(Ignore the 1.12.1 part -- it works just fine on 1.12.2)

Thanks for the answer! I'll try now.

All OK, thanks!
But I can't find this lib as jar file on curseforge (for modpack).
Can you also add this dependency into wiki/readme?
You can close this issue.

The jar is embedded inside the guidebook jar, it is extracted on demand by forge's dependency extraction system. If you open the guidebook jar in winzip/winrar/7zip or whatever app you use, you'll see it's there inside META-INF/Libraries

It's strange, why it does not happen when the client is launched through the IDE.

I do not really know why, sorry. I think it has to do with how forge works with embedded jars, but it's just a guess.