wingsandsword
Legend
The idea of everyone being literate except Barbarians was a 3e invention.Literacy. D&D (except barbarians in AD&D) assumes that everyone, even peasants, are literate in every language they speak. Literacy in the West wasn't even that common among the aristocracy until the Renaissance, kept mostly to the priesthood. Books themselves shouldn't even be common unless the printing press is, and it's never mentioned anywhere, except in the FR (possibly Ebberon, but not familiar).
There was NOTHING explicitly in AD&D that I'm aware of saying otherwise. It was an incredibly common house rule that Wizards (and usually Clerics) got Read/Write NWP for free, but it wasn't in the core rules-as-written.
I even remember a Scale Mail letter in Dragon Magazine asking how a Wizard could use a spellbook if they didn't automatically get Read/Write, and the answer was to say that magical notation for spells wasn't the same as literacy and that reading a spellbook would be like reading music, an entirely separate notation that is a separate skill and you could know how to read one without understanding the other.
I even saw it pointed out that one of the flaws in the 2e NWP system is that it would take two NWP slots for a Fighter to learn Read/Write because it wasn't in their NWP groups, and if they didn't know it at character creation it would take numerous levels to get two NWP slots to be able to spend on reading and writing, long enough that in a low-power game they might never even learn.
If I'm wrong, and I may well be, I'd love to see it pointed out with a quote from the 1e or 2e core rulebooks that AD&D had universal literacy.