Rainsford is surprised and impressed at general Zaroff's sophistication. I don't blame him. They are on a remote island. In light of this, Rainsford is probably surprised that there is life on the island, let alone a person who is as sophisticated as general Zaroff. We must also bear in mind that the general knows how to speak several languages, knows about fine foods and wines, and has even read Rainsford's books. This is what the text says:
"Not in the least," declared Rainsford. He was finding the general a most thoughtful and affable host, a true cosmopolite.
That said Rainsford is not completely comfortable. Something about the general makes him feel uncomfortable. Here is what the text says:
But there was one small trait of .the general's that made Rainsford uncomfortable. Whenever he looked up from his plate he found the general studying him, appraising him narrowly.
Finally, when Rainsford learns that Zaroff is hunting humans, he is disgusted with Zaroff.