Barbara Ninde Byfield’s The Glass Harmonica, later released as The Book of Weird, is the best book you can get about traditional fantasy. (Which is not to say “vanilla” fantasy. Traditional fantasy is Dunsany or Tolkien or the Lang Fairy Books, vanilla fantasy is Inspired By Tolkien and is uniformly bilgy, unbearably so if it’s actually inspired by D&D.) You could very easily run a fine D&D game by plopping down with the Basic set and a copy of Harmonica.
I just ran across this original ad, which I suspect distills the 1967 fantasy zeitgeist into its full potency.