Three aspects of the narrative really struck me.
First, that the candidates themselves tend to be pretty flawed human beings. Successively the Edwards and McCain campaigns crashed to disaster largely because of the personalities of Edwards and McCain themselves, unwilling to adapt to the discipline necessary to keep their teams motivated and to avoid gaffes to the press. Both Obama and McCain suffered serious wobbles in the last few weeks before the election due to the indiscipline of their running-mates. All of those individuals had previous won elections for public office, so it is surprising that Edwards and McCain were not able to deal with the demands of the presidential campiagn. I can cut Biden and Palin a bit more slack, as the vice-presidential slot is much more peculiar, and perhaps Edwards is explicable because he was in complete denial about the state of his marriage. But McCain's behaviour is just bizarre.
Second, and linked to the first point, the peculiar desire of the media - particular the US media - for spectacle rather than story means that any electoral campaign is vulnerable to a single killer moment. Occasionally - as with Hillary Clinton's tearful interview in New Hampshire, which it is pretty clear won her the primary there - it works to the candidate's advantage. Much more often, of course, it reacts to their disadvantage, as Rick Perry is discovering.
Third, and also linked to the first point, the fact that the US system is so very candidate-based rather than party-based makes the professional campaigner's career much more volatile and much more based on personality. That has consequences for how campaigns work internally. Staffers are jockeying not only to get the credit for getting their candidate elected, but also for positioning in the victorious candidate's administration and/or for a better-paid role in the next campaign. It can also be much more difficult to tell the candidate home truths about their own performance, compared to the situation if both candidate and staffer are beholden to a political party structure rather than staffers being utterly dependent on the candidate's whim. It also feeds into the dependence of the campaigns on continual fund-raising.
In the end, Obama won because his fundamentals were sound; he had a good narrative in the first place, he was disciplined about sticking to it, and he was fortunate in both the character of his opponent in the general election and the economic circumstances which made Republicans unelectable in 2008. Clinton was unlucky in that her narrative was almost as good and her discipline equal to Obama's, but her campaign team was less coherent (for the reasons given above) and she carried unfair negative baggage in the shape of her husband. McCain lost because he deserved to. (The authors are surprisingly sympathetic to Sarah Palin, and blame McCain for choosing her without sufficient forethought and exposing her on the national platform without adequate preparation.) An excellent book from which I learned some interesting things.