The differences and similarities in both Go Tell It on the Mountain and To Kill a Mockingbird are often intertwined with one another. The two share similar themes and conflicts while going about the presentation of them in vastly different ways, mainly due to the racial, gender, and cultural gaps between John and Scout, the respective protagonists of each book.
Both Go Tell It on the Mountain and To Kill a Mockingbird are bildungsromans. A bildungsroman is a coming of age novel charting the protagonist's formative years, usually in regards to moral or spiritual development. In Baldwin's novel, the protagonist's spiritual development is a heavy theme: John goes from anguish and doubt regarding religion to belief in God, even if the novel's vision of Christianity is an ambivalent one, showing it to be a religion marked by hypocrisy and fear as much as grace and redemption. While religion plays no such role in To Kill a Mockingbird, Scout's awakening to the injustices of the adult world and her final kindness to Boo Radley are formative experiences, pushing her from innocence to knowledge.
The two novels also share a setting: the American South of the 1930s. Due to the prejudices and culture of said setting, both novels also deal with racism against Black Americans, though the way the reader sees said racism is different due to the viewpoints from which each story is told. Go Tell It on the Mountain has a Black protagonist in John, so the reader sees how prejudice affects its victims firsthand, while To Kill a Mockingbird shows prejudice from the viewpoint of a social majority in the white Scout.
Finally, both novels have the protagonist experience some level of alienation due to a part of their identity. John is a gay young man in a Christian community wholly opposed to his sexuality, and Scout is a tomboyish young girl in a society where girls are expected to behave in traditionally feminine ways.