It's mainly about a girl's journey in a marriage. It shows how she overcomes difficulties and finds happiness within the marriage. There are elements of character growth and relationship building in the story.
I'm not entirely sure without reading it fully, but usually in a marriage - centered novel, there would be the husband and wife as the main characters.
The 'My Happy Marriage' English light novel likely focuses on the relationship between the main characters in the context of marriage. It could involve their daily interactions, how they overcome differences, and build a loving and harmonious relationship over time. For example, there might be stories about how they support each other in difficult times, or how they come to understand and appreciate each other more deeply.
It's a novel. The structure and style of My Happy Marriage indicate that it originated as a novel, not a manga. The depth of character development and the complexity of the plot are typical of a novel format.