First published in 1965, Philip José Farmer's The Maker of Universes is the start of an entire series of pulp fantasy books generally called "the World of Tiers." These stories are very much in the mold of Edgar Rice Burroughs' Barsoom novels and other similar stories, in which a man from 20th century Earth is transported by mystical means to another world in which he finds himself uniquely strong, intelligent, and irresistible to the exotic women of his newfound home.
It's classic wish-fulfillment fantasy, but there's no denying that Farmer has a real knack for it. The Maker of Universes describes the adventures of Robert Wolff, an aged World War II veteran and linguist, leading a dull and unsatisfying life, who discovers a doorway to the World of Tiers -- a series of artificially constructed worlds stacked on top of each other, at the topmost level of which dwells its Lord, who rules it (and may have created it). Upon arriving in the World of Tiers, Wolff regains his youth and vigor and sets off to overthrow the Lord and end his tyranny. Along the way, he has many unusual adventures and meets a cast of memorably quirky characters, some of whom return in later novels of the series.
I don't recall any specific elements from this book that turned up in Dungeons & Dragons, but the general tenor of the novel certainly matches the pulp fantasy tone that I contend is at the heart of the game. In addition, it's another example of a story involving a fantasy world connected to our own, a common theme among the books Gary Gygax cited as important influences on him and the game. The more I think about it, the more intrigued I become about what this means for interpreting D&D and the Gygaxian conception of it. I'll probably return to this theme in a future post. For now, though, I can't shake the feeling that there's more going on here than meets the eye.