A theme found in both books is the hypocrisy of self-righteous society. Both books represent corruption of the American dream.
Huck and Nick are both outsiders in the society they are trying to observe. In The Adventures of Huckleberry Finn, Huck is the son of the town drunkard who tries to learn to be civilized. In The Great Gatsby, Nick is an outsider experiencing the life of the rich and privileged.
Both of these stories capture different aspects of the American dream, and highlight its hypocrisy. Huck experiences the tyranny of religion over people’s lives, and Nick experiences the tyranny of wealth.
Nick comments on how Tom and Daisy flit in and out of people’s lives and destroy them, never feeling the effect of things themselves.
They were careless people, Tom and Daisy -- they smashed up things and creatures and then retreated back into their money or their vast carelessness or whatever it was that kept them together, and let other people clean up the mess they had made." (ch 9)
By the time they do pay the consequence, everything has been destroyed.
Huck likewise feels frustration and confusion over what society does and does not accept. He considers himself dishonest for helping Jim escape, when in reality his conscience is telling him that it is wrong when he sees Jim as a perfectly nice guy who is a good friend and really loves his family.
The most serious hypocrisy Huck sees has to do with religion. An example is the Shepherdsons and Grangerfords, who kill each other six days a week and then go to church together on Sunday.
It was pretty ornery preaching—all about brotherly love, and such-like tiresomeness; but everybody said it was a good sermon, and they all talked it over going home, and had such a powerful lot to say about faith and good works and free grace and preforeordestination …. (ch 18)
Throughout the book, Huck sees examples of religion perverted to meet different people’s needs. As with other aspects of society, the people who are supposedly in the right are not the moral and just ones.
The corruption of the American dream is a common theme in American literature. We see it represented here in two forms and two eras, both with outsiders as narrators.