As a game master, I want material to place into a structure of play. Factions for a fish tank, for example. I don’t want to study, and I don’t want static information, like X hates Y or Z owns [this and that]. I want to create those relations, but get inspirational injections from the setting material.
I also want to know about everyday things that happens. Things people say, clothes they wear, views of life. This can be told through the game mechanics, rather than the world, which means that the players will read about it while making a character.
I don’t want the setting to be a chapter of it’s own, but to breathe atmosphere into the other parts of the game. To constantly feed a mindset all through the book.