The tone and mood of "The Most Dangerous Game" is suspense. Each situation is set up to provide the maximum amount of fear and anticipation in the reader, from Rainsford's initial fall off his ship to his discovery of Zaroff's true purpose and the knowledge that he will be next in the hunt. Richard Connell uses simple and direct language to evoke an almost black-and-white world, with a protagonist and an antagonist, but allows for subtlety in motivation and event.
...sleep did not visit Rainsford, although the silence of a dead world was on the jungle. Toward morning when a dingy gray was varnishing the sky, the cry of some startled bird focused Rainsford's attention in that direction.
(Connell, "The Most Dangerous Game," classicreader.com)
This comes after Rainsford uses his hunting skill to lay a false trail; although his skills are obvious, he is still wary of Zaroff's own abilities, and in his tree, he is unable to relax because of his fear. The reader is meant to feel the suspense of his situation: will Zaroff find him or will he be able to escape? Each situation that Rainsford finds himself in increases the suspense by letting him barely escape until the end.
The mood seems to me to be somber, eerie, uncanny, sinister, even surrealistic. If the reader identifies with Sanger Rainsford and really gets into the story, the reader will feel on the verge of panic. Rainsford is cut off from the world, marooned on an island ruled by a madman who is an expert hunter and kills human beings for sport. The island is dark and uninhabited except for Zaroff and his small staff. Even in the daytime the island seems dark because all the heavy tropical vegetation cuts off so much of the sunlight. The reader has no sense of direction. Zaroff knows every inch of the island, but the reader, identifying with Rainsford, knows nothing about the setting. There could be traps everywhere. Rainsford cannot move without leaving footprints for Zaroff to track and his scent for the hounds to follow.The mood seems similar to that of Edgar Allan Poe's "The Pit and the Pendulum," in which the viewpoint character is helpless, frightened, unable to see, subject to horrible imaginings, at the mercy of merciless captors. Perhaps the best term to describe the mood of "The Most Dangerous Game" is "a living nightmare."
the mood is the readers feelings toward the novel. In this story it could be many things....fearful, mysterious, suspenseful etc...