Their Eyes Were Watching God is, primarily, a coming-of-age novel. The book is structured around Janie's three marriages, through which Janie establishes her own independence, maturity, and identity as a woman. The book is not, in terms of genre, a romance novel: the story is not about the acquisition of a partner, or even about the acquisition of the three partners Janie has throughout the book. Instead, the book is about the effect those three partners have on Janie as she comes to understand herself better and learns how to interact with other people and the world.
The book shares some classic qualities of the long tradition of the English novel. Hurston calls back to various forebears: the novel's frame story recalls Conrad's Heart of Darkness; the contained settings with controlled movement from place to place recalls Brontë's Wuthering Heights; the heroine learning through love interests with various imperfect men recalls the structure of Austen's novels.
The book is not, notably, a book about racism. There are, indeed, very few white people in the book at all. There is discussion of racism: Nanny is especially aware of it, having grown up in the time of slavery. But Janie quickly dismisses Nanny's worries about her granddaughter's life. The most explicit racism in the book is in Janie's trial, but even there, it is the favor of the white women that gets Janie acquitted. Their Eyes Were Watching God is a book about Black people and their lifestyle, culture, language, economy, and romance in the American South in the 1930s. But it is not a book about race and not a book about racism. So the book cannot be counted in the important genre growing in America at the time, of African American protest literature, typified by the work of Richard Wright and expanded in later decades by Ralph Ellison, Alice Walker, and Toni Morrison. Hurston was criticized at the time, most notably in a highly-publicized feud with Wright, over her unwillingness to comment in her novels on racism and politics. Still, the novel stands as a special kind of advocacy: by writing a coming-of-age novel, full of romance, about her people, Hurston argues that Black people have as much of a claim on the genre as white people.