Discussions of Steinbeck's writing style in this novel will include the decision to use non-narrative chapters between the narrative chapters, heavy use of dialogue (and monologue), a concern with social issues/themes and a visually oriented prose.
Steinbeck's prose is highly visual in its focus in both the narrative and non-narrative sections of the the novel. (This trait is emphasized in the non-narrative sections). There is also a heavy use of dialogue throughout the novel. Much of the story is taken up by discussion and in the narrative sections of the novel it is in the diaologue sections that many of the themes and concepts relating to social justice, inequity, religion, and morality are discussed.
One of the most remarkable and unusual features of this novel is the use of non-narrative chapters. These chapters represent less than half of the novel in terms of the number of pages dedicated to them, but represent roughly half of the numbered chapters in the book. These sections present a pastiche of the novel's themes and serve to connect the Joad's plight to that of a whole class of people.
Aside from the heavy use of dialogue and visually oriented details, Steinbeck's prose employs idioms frequently (within the dialogue) and simile. In terms of figurative language, simile is used more often than direct metaphor, perhaps because simile better reflects that kind of language used in the speech of the people Steinbeck is writing about in the novel.