Autobiography; Coming-of-Age; Family Drama
So Go Tell it on the Mountain isn't a straight-up autobiography; it's definitely fiction. However, there are lots of parallels between John Grimes' life and James Baldwin's, and they're pretty well-known. Most critics consider the novel to be at least semi-autobiographical because of those details that match up between the real author's life and the protagonist's (for example, Baldwin's mother married a preacher who adopted him and treated him pretty badly).
Johnny undergoes a huge transition over the course of the night in the novel. He turns fourteen, for one thing, and he is "saved," for another. These two events catapult him from childhood into some version of adulthood, where he's expected to straighten up and fly right. The focus on this transition makes the book a bonafide coming-of-age novel.
Finally, there aren't many families with more drama than the Grimes. Between secret children, secret fathers, and secret mothers, it's all sick n' twisted. The novel is built up around these secrets and lies, mostly to get at John's origin.
Let's unravel it quickly: John's father hates him because he's not his biological son; his mother has never told him that she had him before she met Gabriel, because she's ashamed; Gabriel married Elizabeth and adopted John to try to make up for the deaths of Esther and Royal, his first son. Phew. We're going to need a family-drama detox after that.