Dark romance is a subgenre of literature that combines dark themes with the traditional framework of a romance novel. They explore morally ambiguous characters and taboo relationships and themes. While traditional romances highlight love and companionship between two characters, often using conflict to drive growth and romance, dark romances focus on trauma, violence, and explicit sexuality. Notable examples of dark romance include Haunting Adeline by H. D. Carlton and Lights Out by Navessa Allen, each of which embrace a mix of violence and sexuality to create intense love stories between the main characters. Dark romance borrows themes and elements from horror, thrillers, and even paranormal literature. They also introduce tropes and elements from romances, including enemies-to-lovers narratives, betrayals, and happily-ever-after (HEA) endings.

The Sinner falls into the dark romance subgenre by virtue of its intense and dark themes, including trauma, abuse, and violent sexuality. Elli’s past trauma triggers her affinity for violent sex. This, as well as Sin’s desire to “own” Elli through degrading sex acts, are common motifs in dark romances.

Many dark romances exploit the ambiguity between non-consensual assault, dubious consent, and consensual sex. The Sinner uses this trope, with Sin occasionally crossing the line into sexual assault with Elli. The Sinner features intricate sexual play, with some readers asserting that the sexuality of the novel overwhelms the plot of the narrative. As with many dark romances, The Sinner concludes with an HEA (happily ever after) ending, in which Sin and Elli continue their sexual play long after the conclusion of the conflict.