A great portion of the book is devoted to dams. The gist of it is that many dams of questionable utility were constructed throughout the 20th century due to pork barrel politics and the unstoppable bureaucratic engines of the Bureau of Reclamation and the Army Corp of Engineers. Like much infrastructure built in the US, not much concern was given to ongoing maintenance and so the book predicts that this will be a larger concern as time goes on.
Hopefully close calls like Oroville will bring more attention to this issue before a larger disaster happens.