Jonah follows the transformation of a physically disabled, street-hardened youth as he navigates the volatile social landscape of early 20th-century Sydney. Jonah begins his life as a member of a larrikin gang, defined by his hunchback and his ruthless ambition to escape the poverty of the slums. He must contend with the rigid social hierarchies of the city, the influence of his mentor-like figure Mrs. Yabsley, and the complexities of his own evolving morality. The narrative employs a third-person perspective to detail the gritty reality of urban life and the eventual rise of its protagonist into the world of commerce.

This novel is widely recognized as a foundational work in the canon of Australian urban literature. Critics frequently highlight Stone's ability to render the specific sensory details of Sydney's environment with precision and sensitivity. The work is often discussed for its departure from the bush-centric narratives that dominated the period, offering instead a grounded look at city life. Readers and scholars alike note the balance between the harsh realities of the slums and the personal growth of the central characters. The text remains a significant reference point for understanding the social history of the city at the turn of the century.