The Great Gatsby
1.The way it was explained to me is that Nick is not directly involved in any of the drama that is happening. He is a reliable narrator and we can trust what he tells us. He observes what happens between Gatsby and Daisy without his emotions clouding his judgment. There are books where the narrator telling the story outright lies to the reader, and gives false information. Nick is not one of these narrators. He is the only character in the story who can tell us what is happening without bias, because all of the other characters are emotionally involved with each other.
2.nick does not like Tom because Tom is an arrogant, hypocritical bully. His social attitudes are laced with racism and sexism, and he never even considers trying to live up to the moral standard he demands from those around him.