Wait, no one read the 1e DMG? I've read that thing cover to cover a hundred times. Even with Gary's rambling and alternating from "this is your game" to "if you don't play according to these rules, you're not playing D&D", the wealth of content in that book is amazing and I love to refer to it today.
Sure, there's some "screw over your players, they don't deserve class abilities", but there's a random dungeon generator, lists of herbs and gemstones with possible magical abilities, a list of ecclesiastical titles, a dissertation of many different types of government, magic items, artifacts, games of chance...it's a treasury of information, unlike, say, more current versions of the DMG.