English project - 3 books with a theme?

I'm doing a project for my English cl where I have to read 3 fiction novels with the same topic or theme. I decided to do human nature and I came up with Ishmael by Daniel Quinn, Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson, and The Man that Corrupted Hadleyburg by Mark Twain. After going to buy The Man that Corrupted Hadleyburg I saw that it's more of a short story. Could it be considered a novella? And do you think I could come up with a decent paper about human nature with these books? I'm really not sure where I'm going yet with what I want to learn from the books but I just looked up "books about human nature" and these were what I found most interesting.