Another possible theme could be the struggle against fate. The characters in the 'Heart of Glass Novel' may be constantly trying to break free from the predetermined paths that fate has set for them, and their 'heart of glass' represents their vulnerability in this struggle.
Another possible theme could be the struggle between reality and illusion. The 'heart of glass' may represent a state of mind that is not fully in touch with the real world, and the story could be about the character's attempts to break free from this and face reality.
The main theme could potentially be self - reflection. Being in the glass booth, the man is in a very exposed yet isolated situation. This might force him to look inward and examine his own identity, actions, and values more closely. He is in a sort of liminal space where he can be observed by others but is also alone with his thoughts, which could lead to a deep exploration of the self.
The main theme could be about the search for truth or self - discovery. Often in such novels, characters are trying to understand the world around them and their place in it, which might be blurry like seeing 'through a glass darkly'.
I'm not sure as I haven't read it, but it could be about the life of a duchess in a particular setting, perhaps with themes of luxury, power, and the challenges she faces in a glass - house - like environment which might symbolize fragility or transparency.
Perhaps there is an older, wiser character who serves as a guide or mentor to the more troubled main character. This type of character is common in novels and could play an important role in helping the main character deal with their 'heart of glass' - like state.
I'm not sure specifically as I haven't read the 'Heart of Glass Novel' in detail. But usually, there could be a protagonist who drives the story forward. It might be a young person, perhaps a girl, who is at the center of the events in the novel.
One of the main themes could be the search for truth. Since seeing 'through a glass darkly' implies a somewhat obscured or unclear view, it might suggest that the characters are trying to find the real meaning or truth in their lives or situations.
The main theme could be self - discovery. In the story, the looking glass might symbolize a tool for the character to look inward and understand themselves better.
The main theme is survival and family. It shows how the family in the story endures difficult situations, both financial and emotional, while still being a family in their own unique way.
The main theme is probably kindness and the power of a small act of giving. The glass of milk could symbolize the basic human compassion that can have a big impact on someone in need.