Since they were added mid-development, the library doesn’t have any mention of classes. I know there isn’t terribly much to say about them, but at the least the section on spells should mention something like “Spells from your class’s realm are more powerful.”
For a larger suggestion that might not be worth the time it would take, it would also be cool if the section about kingdom upgrades you’ve purchased had more information about the upgrades you’ve purchased. Like, a short description of the types of things likely to be found in each of the types of realm? Or which artifacts each blacksmith upgrade unlocked, or maybe a bit of mechanics information about what the transmutation upgrades do, etc.