Well, I think the theme of illumination, in a metaphorical sense, runs through the novel. It's about finding light in the midst of darkness, whether it's understanding difficult family secrets or coming to terms with one's own place in the world. The characters face various challenges and through their experiences, they gradually gain a new perspective, which is like being illuminated.
The main theme could be about the search for truth and identity. The characters often embark on a journey, both physical and emotional, which leads them to discover things about themselves and their pasts.