The Jungle has a uniquely somber and bleak tone throughout, offering a critical commentary on societal norms and the wealth disparity of early-1900s America. Sinclair’s third-person omniscient narrator takes a journalistic and factual approach to the book’s gruesome events. They relate most of the book's early material with an air of detachment. For the most part, they deliver a sober account of the characters' experiences, providing readers with a realistic depiction of their struggles and hardships.
As the narrative progresses, the narrator’s tone becomes progressively more involved and indignant. Sinclair's critique of social and economic systems becomes more evident as the narrator increasingly exposes exploitation and injustices. These are perpetuated by tyrannical industrialists, a corrupt police force, and an economy where everyone must fight to survive. The novel takes on an intensely didactic and instructive tone by its end, seeking to educate readers about the political and economic realities of the time.
The Jungle has a strong socialist message, directly telling the reader that capitalist greed and corruption are the central reason for the cruelties that life inflicts on Jurgis and his companions. Through the narrator's voice, Sinclair imparts his own political views, encourages his readers to question the status quo, and advocates for change in the political systems that cause inequality. Much of the novel’s tone served as a call to action for Sinclair’s readers, urging them to recognize and address many of the systemic problems of their historical moment.