The last sentence of this book speaks volumes: "Sometimes you can tell more truth through fiction."
The basic point is this: Our technological infrastructure is woefully underprotected, and a terrorist organization with enough resources would be able to bring not only our country, but the world itself, to its knees with a few well-placed explosives and a series of ones and zeroes.
While reading this book it becomes clear that the author, former counterterrorism czar Richard A. Clarke, is not so much trying to entertain us, as he is trying to warn us. While the story is decent, it is as if Clarke built the story around the underlying warning, like scaffolding around a building. As a result, the plot line is somewhat thin, and the ending anti-climactic. Character development is almost non-existent. Susan Connor and Jimmy Foley are likeable, but we never really seem to get to know them on a personal level. Indeed, any exploration into their personal lives (e.g. upbringing, ideology, motivation, personal relationships, etc.) is stunted and almost entirely peripheral.
Clarke is a competant writer, but he is at his best when discussing the technical aspects of the threat. Had this been a collaborative effort with a more seasoned author, one more adept at storytelling (a Clancy, for example), this could have been a truly enticing and frightening book. As it stands, it is enjoyable, but nothing terribly special.