The story obviously has strong cinematic potential. It was made into a movie in 1932 starring Joel McCrea with the title "The Most Dangerous Game" and an alternative title of "The Hounds of Zaroff." It was remade in 1945 as "A Game of Death" and again in 1956 as "Run for the Sun." A good film with a similar plot but set in Africa is "The Naked Prey" (1966). It stars Cornel Wilde as the man being hunted. Actually it occurs to me that "Butch Cassidy and the Sundance Kid" is similar too.
I would give more background information about Zaroff. I would include several flashbacks throughout the movie to show us how truly scary and evil he really is. I would take the viewer back to his days in the military in Russia. Rather than just glance upon it like the author did, I would show what a difficult time he had dealing with the Russian Revolution in 1917 and the loss of his country. I would connect how this part of his past has helped create the monster that we have before us today. I'd also show clips of him hunting down humans in the most savage and merciless ways showing no remorse or sympathy in his kills.
Any horror story needs the scariest bad guy possible. Zaroff certainly has the potential to be that guy if the director spends enough time developing his character.
One of the things about the story I like is that it is narrated from Rainsforth's point of view and Zaroff's. This omniscience allows us to see Zaroff as a person. Otherwise it is easy to dismiss him as simply evil. If I was directing a movie, I would continue to show both characters' points of view.
I can see vividly in my head the first time Zaroff locates Rainsford. I can just imagine Rainsford having worked so hard to establish a trail for Zaroff to track him that included all kinds of twists and turns that kept him busy. And then, after a moment of great reprieve on Rainsford's part after a climb up the tree, Zaroff's face lightens up with a great and growing smile. Zaroff puffs his cigarette a few times with the knowledge that Rainsford is well above him. But, for the time, to ensure he doesn't get bored again, he allows this game to continue by purposefully pretending not to notice Rainsford. Knowing Rainsford is at the top of the tree, he refuses to look upward and check. I love this scene because it demonstrates weakness in Rainsford who has been such a strong character so far.
I would also love to see the scene played out wherein Whitney and Rainsford discuss the feelings of a jaguar in the very beginning. I think this piece is crucial in the development of Rainsford's character. It shows that Rainsford thinks he is a dominator. That comes to question him throughout the piece.
I would want to see specific details and excitement that i get from reading the book. I would like to see the basic plot but also some twist from you put into it. The fighting scenes should be in there but you could exaggerate them even more which would really make it interesting. Hope this helps :)