Coming of age as a literary subject is not really about age. It is about the moment when a person first understands that the self they were handed is not the same as the self they are responsible for building. That moment happens at different times for different people, and the best books in this tradition locate it not in any particular passage of years but in a specific confrontation with reality — with loss, or violence, or the discovery that the world does not share your assumptions about it.
I Know Why the Caged Bird Sings is the most precise account of this confrontation that American literature has produced. Angelou's childhood — in Stamps, Arkansas, then San Francisco — is not shaped by the usual adolescent confusion about identity, but by the far harder work of constructing an identity under conditions designed to prevent it. The episode with Mrs. Flowers, who gives Maya a book and asks her to read it aloud, is a turning point that most readers recognize even if their own turning point was nothing like it: the moment when something outside yourself shows you what you are capable of.
Housekeeping by Marilynne Robinson is a stranger and wilder coming-of-age story than her later novels suggest. Two sisters, Ruth and Lucille, are raised by a series of female relatives in a small Idaho town after their mother drives into the lake. Their aunt Sylvie arrives eventually and turns out to be someone who leaves the lights off and lets the leaves accumulate indoors and seems constitutionally unable to live in the ordinary world. The novel follows Ruth into that otherworldliness rather than away from it. Coming of age here means choosing, finally, which kind of life is yours — and Robinson is honest that the choice costs something permanent.
Their Eyes Were Watching God by Zora Neale Hurston is officially a love story but is really a coming-of-age novel that takes the full arc of a life rather than just the opening chapters. Janie Crawford's first two marriages compress her into someone's idea of what she should be. Her third, with Tea Cake, is the one in which she gets to find out who she actually is. Hurston's dialect prose — exact vernacular raised to art — gives the novel a sound unlike anything else, and the closing chapters, in which Janie returns home and tells her story, frame the whole book as an act of testimony.
Siddhartha by Hermann Hesse takes the coming-of-age structure and extends it to an entire lifetime. Siddhartha leaves his Brahmin family, experiments with asceticism, then indulgence, then commerce and sensual life, and finally arrives at something like wisdom in the company of a ferryman and a river. What makes the book useful rather than merely inspirational is that Hesse shows each stage as genuinely necessary — the indulgence, the failure, the long slow middle period — rather than presenting a direct path from question to answer. The answer, such as it is, requires the long way around.
A Heartbreaking Work of Staggering Genius by Dave Eggers is coming of age in a different register entirely — postmodern, reflexive, aware at every moment of its own constructedness. Eggers's parents die within five weeks of each other, leaving him at twenty-one responsible for his eight-year-old brother. The memoir is about raising Toph while also being barely finished with being raised himself, and about the way processing grief in public changes the grief. The preface and acknowledgments, which Eggers uses to subvert the conventions of memoir, are themselves a kind of coming of age: the discovery that the genre you were given to tell your story is inadequate, and that you are going to have to break it.
What distinguishes the best coming-of-age literature from the ordinary version is that it does not present the arrival as complete. Siddhartha watches the river and understands something — but what he understands resists summary, and he would not have understood it at twenty. Janie returns home with her story, but the story took forty years to accumulate. The best books in this tradition take seriously the possibility that coming of age is not a milestone passed but an ongoing process of revision — one that, if you are lucky, continues well past the age at which anyone expects it.