My brother collected these. I think he still has some of them somewhere. Like the original boxes for Diablo and Starcraft.
I collected some too, but I think I eventually got rid of mine. I was into the various Maxis Sim games, so I had tons of the boxes. SimCity, SimTower, SimPark, SimIsle...
The best manual was probably Ultima Online, an MMO. I read and studied the shit out of that thing. Used to bring it to school to learn all the spells and stuff. Also came with a good sized, folded-up map of the world on special paper.