Cool. So far, at least. Does it affect the design? If not, it's wasted, IMO.So let’s say my game has a unique creation story that informs all of my world building, the nature of all beings, especially the adversarial beings that threaten everything, and underpins how magic works and what it even is in the world.
If I'm playing a cleric, or if the cosmology includes accessible planes, yeah, I want a nice precis, and, ideally, more to read laterDo you want to know about it, as a player? Do you read all you can, or ignore it and only bother learning the “right now” stuff that directly affects your character?
If it is included past a couple paragraphs, yes.Do you want cosmology to matter, with mechanical weight put behind it?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.