If you are referring to Stephen Donaldson, he received his degree from the College of Wooster, which largely explains the 'arcane' language of his novels.
His writing is reminiscent of the volumes published in the period 1880-1920, aimed at an Upper Class audience; at the time, university graduates would at the least retain a vocabulary including some Greek and Latin words if not the ability to read bits of the writings in those classic languages. The travel literature of the time will exercise even the erudites' skill.

I object to your characterization of the work of Dorothy L. Sayers, and her excellent novels (directed toward an educated audience, leaving the lower orders to Beatrix Potter).
I have been meaning to read her translation of Dante's "Divine Comedy," but I would probably revert back to the the Lord Peter Wimsey stories.

My education and experience at an American university , lacking the refinement to be gained at Cambridge or Oxford or College of Wooster, would leave me unable to hold forth at high table. I am confident that Donaldson would be quite acceptable.

(Wooster students, pay no attention; but the name does invoke thoughts of Bertie Wooster)

Digression- listen to Hugh Laurie, as Bertie Wooster, sing "Forty-Seven Ginger-Headed Sailors." Worth a genteel chuckle or two.
Ginger Headed Sailors