Queen Song is a short novella detailing Coriane’s life. It begins prior to her introduction to the Prince and shows a simpler life. Her elder cousin Jessamine wants her to be a proper lady and help restore the power/glory of their failing house. Coriane Jacos just wants to tinker and build things. It was nice to see that similarity to her future son, even though they never really knew one another.
You also get a taste of a second (future) queen in the young Elara, Maven’s mother. She is just as pleasant as a young adult as she is in the series, which is to say she’s a terror. Elara is manipulative and her power is incredibly strong.