Since I'm not acquainted with this light novel, it's difficult to determine the exact themes. But common themes in such works could be the bond between generations, unrequited love, or the challenges of social interactions. For example, in some similar light novels, the relationship between a parent and a child can play a crucial role in the story, while at the same time, the romantic feelings of the characters are also explored. Without reading 'you like me not my daughter light novel', we can only make these general speculations.
I haven't read this 'you like me not my daughter light novel' yet. Maybe you can check out reviews on websites like Goodreads or Amazon to get an idea of what it's about.