It could be the concept itself. The idea of not becoming a certain type, like a villainess, is different from many traditional stories. This unique premise might lead to unexpected plot twists.
I'm sorry, I haven't read this light novel specifically. But generally, a light novel often features unique characters and an interesting plot. It might be about a character who doesn't want to become a certain type, perhaps a villainess in this case, and the story could revolve around her struggles and adventures to avoid that fate.
Another theme might be identity. The idol has a public identity as a popular figure, but also has this secret virtual - world relationship, so there could be exploration of different identities. And also, the theme of virtual vs. real might be present, as it bridges the gap between the online game world and the real - world idol industry.
The 'netoge no yome ga ninki idol datta ken light novel' might explore the concept of how the two different worlds, the netoge (online game) world and the idol world, collide. Maybe the main character has to deal with the fact that his virtual wife is now a public figure. It could be filled with comical situations, like trying to keep their relationship a secret or dealing with the idol's fans.