Dimensional Librarian

Levi Warwick, a novel author, wakes up trapped in the Library of Noctis a mysterious realm filled with forbidden books. To survive, he must help each patron find the book they seek… or die. The catch? Every patron is a terrifying being Archwizards, Demon Lords, even Demigods. If one of them so much as farts in his direction, he’ll be dead on the spot. He’s just a normal guy. But to them, he appears to be the legendary Librarian cold, powerful, untouchable. So he smiles, lies, and prays they never find out he’s winging it — Description from novelcodex.org