Language, history and curiosities in games.
Well designed rules make for an easier to read rulebook!
My experience is that if the rulebook is a chore to read then the game is likely to be a chore to play.
A successful rule book will be able to explain the rules even without having the game in front of you.
“So the challenge is simple,” I continued. “You and your teammate have five minutes to learn this game and present it to the rest of us. “Oh, I’ve also removed all the rulebooks.” Take that, smart people.
It’s tough to read a rulebook over and over and only see what is actually there.