The challenge: Recently speaking with a newly acquired friend we found
ourselves speaking of literature. He had mentioned a book he had read a
while back but never got to finish. And since he has recently helped
me I'd like to return the favor. Now I'm not exactly a beginner when it
comes to research, however with the the lack of retained information
gathered I have spent much time searching to no avail. So now I turn
to one of you. This is what I have to work with: A fictional story of
a rich man who's eccentricities  might mention walking about his
property naked. At some point he winds up purchasing a Gorilla which he
lives with. I believe the Gorilla becomes ill and the character calls
a vet/doctor. While the beast is restrained or perhaps just drugged on
an examination table he notices how much she resembles a human female.
And its about this point that my information ends. I have used many
search engines and sites, perhaps my information is just too limited.
In any event, good luck.

This is a long shot:

"One of the key characters in HANGMAN?S NIGHTS is Alfred
Crofts-Hartley, an erudite Londoner with a passion for classical
antiquity who... is the offspring of a female gorilla and a New York
millionaire."

http://www.ramblehouse.com/hangmansnightschapter.htm