Gary Gygax didn't specifically list the 1963 Andre Norton novel, Witch World, as an influence on Dungeons & Dragons in the Dungeon Masters Guide, but I find it hard to imagine he hadn't read it. And while I wouldn't argue that the book was the primary inspiration for anything in the game, the general tone and setting of the novel are very much in line with the older pulp fantasies that did inspire Gygax and Arneson.
Witch World tells the story of Lt. Colonel Simon Tregarth, a dishonorably discharged World War II soldier, who runs afoul of organized crime and finds himself running for his life. Through the agency of a man renowned for helping people "disappear," Tregarth finds himself transported to another world, one where magic is real and strange cultures abound. This world gives Tregarth a second chance at life and he embraces it with great zest, entering the service of one of the world's many nations and falling in love with a practitioner of magic, Jaelithe, with whom he develops an unusual -- and potentially dangerous -- link.
Witch World is very much a descendant of the sword-and-planet genre exemplified by Edgar Rice Burroughs's Barsoom tales and his imitators. Here, as in its precursors, a man from our world travels a parallel one where he finds himself possessed of power and influence unlike any he's ever known. His appearance is literally revolutionary, setting into motion a great change in the established order of his adopted world. The book also freely mixes magic and technology, as the main antagonists of the book are technologically advanced refugees from yet another world. Indeed, Witch World presents a setting in which comparatively few of its inhabitants are in fact natives, with the others having come to it just as Tregarth himself did.
Witch World proved to be Norton's most successful book, spawning not just sequels to the original but all manner of spin-offs, many of them not written by Norton herself. I think many of these later efforts are less "primal" than Witch World and deal with stories and themes that I frankly find uninteresting and that aren't particularly inspirational for the kind of D&D games I prefer. But the original remains a classic and is well worth a read, if you haven't done so. Andre Norton was a very fine writer and her best tales are rightly regarded as among the best in the genre. Witch World is one of them.