From what I've heard they really did have lots and lots of books like in the comic. And were jealous of colleagues that had even more.

Before the books, the world of computing was small enough you probably picked stuff up by having a personal relationship with the other people using that specific mainframe, and the vendor of the mainframe. Before that, you were on the team that build the experimental electronic computer for your institution anyway. And then there's Conrad Zeus, I guess.