Has anyone investigated this art form from Poland? Hands down it's phenomenal! Polish artists used poster art as a means of artistic expression by interpreting and commenting on the subject (usually a movie or play) of the poster. They tied it into a reflection on their society which was the communist Polish People's Republic (1950s to 1980s). The graphic design is amazing. There is a Warsaw Poster Museum that contains Polish posters going back to the 19th century.
The museum of posters in Warsaw is small but worth a visit. Occasionally there are larger exhibitions at bigger museums and galleries.
You can quite often buy them in good condition and I'd guess (being finite) that they might be a good investment for the future as well as nice to have framed in you4 wall.