My games are most heavily and directly influenced by the worlds and stories of two authors: Laurie J Marks (Elemental Logic series) and Ursula K Le Guin (Earthsea series).
My games set in the Forgotten Realms also draw heavily on the world-building, tone, and narrative approach of Erin Evans Brimstone Angels series.
Also, Michel Foucault (Who is a french philosopher, not a fantasy author, but his work has had a lasting impact both on my world building as a DM, and my approach to the game as a player)
(Okay yeah, also Tolkien a little bit, but just The Hobbit, not any of the heavier stuff.)