The most visible theme is jealousy, but the book is less about Capitu's adultery than about the construction of an accusation. The reader receives all the material from Bentinho's hands, who is at once narrator and accuser, and the novel is built so that this condition becomes visible without ever being stated.
Other themes are organized around this. Memory: Bentinho tries to recover the past with a copied house and a book, and the project fails. Appearance and reality: the eyes, the photograph and the resemblance always admit more than one reading. Loyalty and betrayal: the book puts loyalty to the test, and what is known of José Dias, Dona Glória and Escobar arrives through Bentinho's gaze. Religion, which appears as an economy of debts and exchanges, beginning with Dona Glória's vow. And language and narration: whoever defines the words decides what the others see.
That is why the question "Did Capitu betray him?" works as a trap: to answer it already accepts the dossier assembled by one of the parties. The book asks the reader to notice how the accusation was built.