I think it went on too long for a book revolving around a few simple ideas, but it was ok. However the authors do not go far enough. They wrote an update talking about how independents and youth also lean democrat so that is also going to give bigger majorities.
http://www.prospect.org/cs/articles?article=back_to_the_future061807There are other trends that favor the dems that aren't addressed:
A lack of economic security will push people into the dem catagory, and also give birth to a new union movement. When 20%+ of hte public are in unions it'll help the dems out alot.
The country is becoming more secularized and less religious right.
The country is becoming more urban and less rural.
The south is supposedly changing due to immigration from other parts of the country, higher voter turnout among liberals there and a less radicalized youth vote. So even their stronghold in the south may start to crumble in the next decade.
The nuclear family is breaking and there are alot more common law relationships, gay relationships, lifelong singles, divorcees etc. all of which lean democrat.
Fundamentally the GOP of today is a party of white, financially secure upper middle class, married (with children), rural voters. Every one of these demographics is falling apart and shrinking while their opposite is coming up. We are becoming a non-white, economically insecure, non-traditional familied, urban nation.