Brandon Sanderson probably most embodies this, with his extremely rules-defined magic systems.

I think it comes down to the fact that, when you fall in love with a world or setting, you want to understand everything about it.

So if you love Arrested Development, you watch the deleted scenes, you read some critical analyses, you check out that article of "52 Jokes You May Have Missed in Arrested Development" (Did you know that it's hinted that Tobias is an albino African-American?)

If you're really into Star Trek, you get really into the histories of the characters, and how things work, and the science behind it.

And the worst/best part of this is, the cycle feeds upon itself. If Brandon Sanderson posts an author's note mentioning that there are actually a handful of Allomantic metals that weren't mentioned in Mistborn, then fans come up with even MORE questions, and hypothetical, and fan fiction, and so on.

On the one hand, stuff like that definitely grows and strengthens your audience. If you have a layered work, with little details that reward a careful reader, and it shows that you've thought out your world well... well, that's cool! I know we like to rag on Wheel of Time, but no one can deny that when you do your first reread of the series, you're pretty much guaranteed to notice things you hadn't the first time.


I don't think stuff like this is required for a fantasy novel/movie/whatever to be enjoyed, but it definitely helps.