Before you start a game, how much will you read before you just ignore it? Either as a GM or player?
I'm sure some people have no limit. If the GM said "Hey guys, we'll be playing a game set after The Stand starting next month, I want everyone to read it before we start, even if you read all 1,100 pages a decade or two ago." they'd jump at it and be perfectly happy.
To the other end I've been in games with players who completely ignored 2-4 page world overviews the GM had written up. I had one player in my big epic fantasy homebrew world who completely ignored the entirety of the player's handout I'd written up, about 10-15 pages of world info once you took out the pictures.
Currently I'm starting up a new Orpheus chronicle, and one of my players surprised me by getting completely sucked into the setting and just devouring the world info in the main rulebook.
For me, as a player I'm pretty cool with 20 pages or so of world info, more if it's interesting, less if it's overly confusing. As much as I dug Eberron, when we played it no one could remember the names of the different cities and countries and factions and craziness, and I really think starting smaller would have helped us all. As a GM I dislike getting more than 1 page per player of background. More than that just tends to obfuscate the main points IMO.
Anyway, how about you?