Good question. It's been over twenty years at this point, and we skimmed a lot of texts in the classes I took. The one that actually stuck with me was Erving Goffman's "The Presentation of Self in Everyday Life", but I don't know how much that would still resonate.

Emile Durkeim's "Suicide" is famous in sociology because it helped kick off the entire field of study. It was, I think, one of the first works to consider how a profound individual action (suicide in this case) might be largely determined by the surrounding social structures.

I don't know what a good introductory book would be.