This really is an enlightening book. What it does do, is explain what goes on in a particular aspect of any family - she explains how family arguments and conversations work, why some things are said but other left unsaid, and provides some suggestions and advice for going back and fixing some of those misunderstandings. She provides a really comprehensive overview of whole family setups, organizations, and tons of possible situations.
She doesn't say "here's how to fix your problems - they shall all be solved". She can't - she's not your own psychologist. But there is so much information to work with, that for a majority of families this will definitely provide a really good and solid basis for reconciling, and even allowing family members to start talking to each other civily again.
Tannen has done tons of research, and provides many examples from all types of families throughout the whole book - grandparents, partners, families with children, families without children, cross-culture families, etc.. I do have to completely agree with another reader that the examples Tannen gives could have been plucked straight from my life. I found one line in particular that could actually explain away years of misunderstanding between two whole branches of my family, myself included. It's also a very fast read - I read it through in just a few days, and I'm a slow reader.
If anyone in your family is even remotely having difficulties talking to others in your family, you should buy this book. I can't tell you how much it's helped me already. Had to buy two more copies of the book for other family members to "borrow".