My German book keeps switching between "Sie" and "du". How do I fix it?

Set the form of address once and BookyAI enforces it everywhere. For a new book, an "Addressing the reader" option appears under the language whenever the chosen language distinguishes formal and informal address (German Sie/du, French vous/tu, Spanish usted/tú, Italian Lei/tu, Dutch, Portuguese, Polish, Russian and many more): choose Formal, Informal, or let the AI pick one — in every case the same form is used in every sentence of every chapter, and also in appendices, Extend, Polish, Rewrite and translations. For an existing book, open Book details in the workspace, set "Addressing the reader", and regenerate or polish the chapters you want corrected. In fiction, characters still address each other according to their relationship; the setting governs how the narrator speaks to the reader.