First caveat, I've not read any books by Talcott Parsons, or Manheim, and there were several sections in this book that were heavy enough in theory to make me give up. Despite these difficult sections, Goffman's style is breezy and interesting enough to make th is book worth reading for a layman.
Roughly, Goffman sets up a model of human interaction that takes most of its metaphors from the realm of theatrical performance. Human interaction takes place between performers and audiences, interactions happen front stage or back stage. This theatrical metaphor is joined by the idea that human actors interact in teams that share similar motives and values. He joins this "team" idea to the theatrical metaphor by emphasizing the difference between performers and audiences.
After laying out his framework, Goffman then uses examples from literature, his own research, and other researchers to illustrate his point. It is in this section that his writing can seem a bit dated. For example, he repeatedly discusses how college educated women will "play dumb" for their boy friends. I'm not saying this doesn't (still) happen, but the example could use somet updating.
One of the main insights that I took away from this excellent book is that humans largely exist as social beings through their interactions with other creatures, and the idea of a person as an "individual" is, itself, largely a construct. This largely contradicts much of the books/music I imbibed as a teen and young adult (Ayn Rand, punk rock, I'm looking at you). It also seems to me that this "dramaturgical" perspective is a thesis that has been widely adopted by the self-help movement. Perhaps I will now explore some of that (voluminous) literature. Perhaps not.
This book is not without it's more disquieting moments. One thought this book led me to is that the important thing in life is the maintaining of whatever appearance one is required to maintaining. So long as that appearance is maintained, what lies underneath (i.e. the traditional concept of self or personality) is effectively unimportant. If we are only what are interactions with others make us, then what we think/feel on the inside and don't share with others, matters not at all.
Goffman himself explains that the dramaturgical perspective is merely another aspect of a larger attempt to explain human action in terms of human INTERaction, but for me, it has great explanatory weight.