In Appendix N (I think it is), Gygax says that inspiration for the game came particulary from REH, Leibner, Vance and Lovecraft. Tolkien is also mentioned as a lesser figure.
I haven't read Leibner - my impression of his stories is entirely from TSR's Lankhmar materials plus second hand accounts. I've read a bit of Vance and quite a bit of Tolkien, Lovecraft and REH.
There is some resemblance beween these suggested approaches to an AD&D dungeon - weighted ropes, poles, soap, etc - and some of the investigative elements of Lovecraft. Even there, though, the resemblance is not that great: investigation in Lovecraft reveals secrets that humankind was not meant to know - not just whether or not a given pile of rags is yellow mould or an elven cloak.
There is no resemblance between these suggested approaches to play and the typical Conan story - Conan doesn't use 10' poles, doesn't map, grabs jewels and runs with them, and then if they transform into living creatures and try to kill him he kills them first! The Fellowship, in Moria, didn't haul out a rope and 10' pole to help investigate the Book of Mazarbul. I haven't noticed any resembance, either, in the Vance I've read, and I'd be surprised if Leibner - which by reputation is meant to be fun pulpish stuff - involves many 10' poles either, as opposed to the protagonists blundering their way into danger and then making good by liberal use of wits, charm and authorial fiat.
For me, then, the disconnect in AD&D is this: why are the classic adventures intended to produce a play experience that so little resembles what is said to be the inspirational material for the game?