It is virtually impossible to study Go Set a Watchman without considering its relationship to To Kill a Mockingbird. If students have not read the latter novel, consider assigning excerpts from it for this unit, or assign Mockingbird before beginning Watchman.
Consider the works of Truman Capote, a contemporary and friend of Harper Lee's who was a more prolific writer. His novels include In Cold Blood and Other Voices, Other Rooms, and he is also famous for the novella Breakfast at Tiffany's.
Consider other authors whose work documents the American South, including William Faulkner and Tennessee Williams.