The central theme of this work is friendship and the power of friendship to overcome (arbitrary) social barriers. This theme is explored in every section of the novel and underpins every major story-line.
Through his friendships, the protagonist Leo is able to face the race oriented challenges of his life, from boyhood to manhood.
...James Baldwin’s lifelong struggle for social justice and equality for African Americans can be seen as developing from his emerging consciousness as a boy...
Stylistically, the novel utilizes first person narrative perspective and a retrospective narrative format.
For more criticism (largely negative), take a look at this New York Times article published in 1968, the year the novel was published. The article is written by Mario Puzo, famous for penning The Godfather. His criticism is aimed mainly at what he perceives to be Balwin's misuse of the first person narrative style and his character's lack of life.
Too many of his characters are mere cardboard. There are scenes that are simply echoes of the literature of the thirties, and they were cornball even then.
Puzo can be excused, perhaps, for his polemic against Baldwin if we take his screed as a positive statement of literary technique and how novels ought to be written. However, this piece of criticism is not pure. It is clearly biased according to Puzo's distinct (and undefended) personal sense of what fiction writing ought to be. Keep this in mind when reading the piece.
Baldwin's work here incorporates commentary art and performance, drawing upon the ironies inherent in a culture that will praise African Americans on stage while maintaining segregation policies in every day life.