I would say the story is about 60% myth-accurate, while the rest is heavily fictionalized. At times, it was difficult to separate actual mythology from the author’s interpretation, especially if you don’t already have background knowledge of Greek myths.
That said, the blend of myth and fiction worked well overall. Reading from Hera’s perspective was emotionally heavy but also very interesting. If you want to reconnect with the “evil wife of Zeus” and see her story from a more human, painful angle, I would recommend this book.