I suspect people in the majority of countries that Westerners & others tend to refer to as "Eastern Europe" really,
really don't like to be referred to as such. It's very much a political term, and one that - even if the speaker doesn't mean it like that - carries certain undertones, which many of us don't like to be reminded of and don't appreciate.
Geographically, the only "Eastern European" country, really, is Russia - everything else that tends to be lumped into "Eastern Europe" is geographically Northern, Central or Southern/South-Eastern Europe. (I think the actual geographic centre of Europe might actually be somewhere in Lithuania - either there or Belarus/Poland.)
And the cultural and historical differences between the countries of "Eastern Europe" are vast - much more so than the differences between Northern European countries, or Southern European countries, or Central European countries. So this adds an extra layer of complexity to lumping together all the countries who were unfortunate enough to be either occupied by the Soviet Union or behind the Iron Curtain in general.
It's not the people of "Eastern Europe" who usually get a say about how various areas of Europe is talked about, though...
Anyway, this is getting rather off-topic, but I do wish you luck in your virtual journey around the world! It sounds like a great idea, and one I might consider some day in the future - for now I'm too set in what kind of books I want to read.