Two important foundational works are Markus and Kitayama's Culture and the self: Implications for cognition, emotion, and motivation, and Triandis' Individualis

Two important foundational works are Markus and Kitayama's Culture and the self: Implications for cognition, emotion, and motivation, and Triandis' Individualism and Collectivism. I am not a social psychologist so I don't have a really simple introduction that I can recommend (due to lack of familiarity!). But I have seen how, in a related field, overly simplistic and un-nuanced applications of what is actually a pretty complicated framework has lead to shoddy research and bad conclusions. That's why I called it out here.