His entire premise is to challenge the notion that "more is better" and recommend generally that we all be a little more neighborly. If you aren't convinced yet that this is interesting stuff, consider that I had a lively discussion with friends just the other night on this very topic, and they certainly are cool.
I think that young people, maybe women in particular, are searching for some alternatives to the usual arguments and agendas. I mean, I follow politics (more than I'd like--I'm married to a political junkie), and I have to confess that I get rather tired of hearing the same stump speeches time and time again. I don't really feel like I fit well into "conservative" and "liberal" categories. This, incidentally, is one of McKibben's points--that a lot of stuff worth talking about doesn't "fit."
Anyway, I picked up the book originally because the Etsy book club will be discussing it this spring. Good recommendation from a great company. Check it out, and visit etsy to jump into the discussion. Or email me your thoughts--I'd love to hear 'em!