The novel focuses on the Lamberts, a dysfunctional family from Kansas whose three children have fled their home town and disappointed their parents in various ways. (For a better summary, go here.) The novel deals with all kinds of dichotomies -- generational, sexual, social, economic, political and geographical -- and how those gaps in understanding and worldviews manifest themselves and create issues for individuals and families. Because their roles shift as the genres shift, our feelings toward the characters shift as well, so a character who seems sympathetic in one chapter seems less so a few later (with a few exceptions). Franzen has something serious to say about modern society's way of dealing with failure and conflict, and what we will do to try to correct the reality staring us in the face, or what that reality will do to correct us (and how we can ride that out or not).
I have to say, though that while I appreciate the novel, it did not speak to me or hold my attention significantly. I did not grow up in the midwest, nor have I lived in the kind of world he describes. I'm not saying it doesn't exist, just that it has not been my experience. So reading a satire of that world was like reading Candide: I can see the satire and the points he's making, but they are targeted too far away from me to sting. Still, some of his points about the modern world and his assessment of how families work, have stuck with me, but more intellectually than otherwise.