I often have a Wikipedia page for some concept or idea open in a browser tab. It gets closed when I'm done with it, so the longer it's there, the more useful it's likely to be. Currently I've had Imagined Community refusing to be closed every time I trim my browser down, so I guess it's a good one to dig deeper into.
Imagined Communities is a model for looking at how nationalism can work across a whole country of millions when we barely know a few hundred of our "fellow citizens". A nation is a socially constructed community, imagined by the people who perceive themselves as part of that group, amplified by the media which promotes a common vernacular language, starting with print moving away from Latin around the 16th century.
The origins are interesting, but what really intrigues me is the fluidity of it all, the fact that something as seemingly concrete as a national identity is really anchored by the shifting sands of language.
I've never felt particularly patriotic or felt an explicit identification with my nation of birth - I get an acute dissonance when people talk about how "we" are doing in the World Cup or the Olympics because I don't really feel any connection with the people on those teams, other than we communicate in broadly the same sort of way. That said, I'd probably struggle to have a nuanced conversation with someone who's life has been totally informed by the culture of sport. We might be physically from the same country but culturally we're on different planets.