The narrative centers on the transformation of an artist's model named Trilby O'Ferrall under the hypnotic influence of the sinister musician Svengali. Trilby, a young woman living in the bohemian circles of Paris, finds her autonomy stripped away when she falls under the control of Svengali, who uses his mesmeric powers to turn her into a world-renowned singing sensation. The story explores the tension between artistic genius and personal agency, set against the backdrop of late 19th-century European art culture. The narrative framework utilizes a nostalgic, retrospective tone, often reflecting on the lost innocence of the characters' youth.

Readers and critics often note the novel's significant cultural impact, particularly how it popularized the concept of the Svengali figure in modern parlance. Discussion frequently centers on the balance between the lighthearted, nostalgic depiction of student life in Paris and the darker, more unsettling elements of the hypnotic plot. Many observers highlight the author's background as a caricaturist, noting how this skill informs the vivid, visual descriptions of the characters. The work is frequently studied for its reflection of late Victorian anxieties regarding gender, influence, and the nature of celebrity. Readers often find the shift in tone between the early chapters and the later, more dramatic sequences to be a defining characteristic of the reading experience.