Langston's character
The thesis of this memoir seems to be explaining the sense that Langston carries about his unique point of view. He argues through narrative that his character drove him in a way that few of his peers chose. His path in life was even unfamiliar and confusing to a father who wanted something different from him. The powerful voice that the author is known as is at odds with the surrounding culture he grew up with. His success seems at odds with his childhood poverty.
Poverty and childhood
The novel exploits a situational irony about childhood poverty. The American Dream frames poverty as a moral problem, because "if you work hard you can make something of yourself"—at least that is the American mythology. But for Langston, poverty was a sign not of moral corruption but of disenfranchisement and racism. As a child in a big city, opportunity is severely limited, and to make something of himself, he must become more educated than those around him. Work seems not to be the answer to his problems. The answer is education.
The ironic father
The father in this story plays a role opposite of one's natural expectations. Father's are typically men who lead and support a child, but in this story the father is largely absent, and when he does arrive, he doesn't understand his own child. He cannot support his child because he does not really approve of Langston's quiet and studious personality. The father is aloof and condescending which further proves Langston's emotional suspicion that he will have to be his own master in life, following his own intuition.
Europe and drama
Traveling through Europe gives the memoirist a broader perspective of the world, as expected, but it also signals dramatic irony within his sense of self. The drama of Europe is largely that he does not know his own self as well as he believed; there was more to him the whole time than he knew. Even though he does not get the chance to travel the whole earth, he can extrapolate from that new knowledge what other surprises he might have within his own self. There is situational irony here too because it is contrary to natural expectation to surprise one's self so substantially.
Fate and choice
Although parts of the novel clearly point to art and literature as Langston's personal fate, he ends the novel by choosing his destiny with commitment, responsibility, and gravitas. He chooses to become a great writer. That is ironic in several ways, but perhaps the most obvious is the irony stemming from his volition. Perhaps the natural inclination is to believe one must be lucky, but in this case, he seems to be arguing that the real "luck" is accepting fate and committing to greatness.