My wife is a dam safety professional, and my sister lives very close to the site of this dam, so I not only knew the basic story of this dam, I had actually visited the former dam site before having read the book. The book tells the basic story about the dam's failure right away, which I think was a good decision, because after that, the author goes into a great deal of detail about the history of Los Angeles and some of the notable people in the story (particularly the dam's designer, William Mulholland), and it takes quite a while to get to even the dam's construction, instead first dealing with the construction of other aqueducts and structures to establish context. During that building phase, I felt like a lot of the detail was extraneous, but just about everything was eventually relevant in one way or another. The personal stories of people caught in the flood are difficult to read, emotionally, but an important part of the story. Since I was reading this aloud to my wife (who is not much of a reader, but was interested), it was particularly difficult. The book then dealt with humanitarian efforts, financial settlements, and legal battles for a while, then dealt with some efforts to understand why the dam failed, and the implications of that failure on a contemporary project, the construction of the Hoover Dam. With that, and coverage of the death of William Mulholland, the book seemed finished, though just under half of it still remained.
Later chapters covered another book from the Sixties that uncovered some inconsistencies in the official story from the utility providers involved in the incident, as well as some unusual later coincidences, and then some much later computer-aided simulations of the dam failure that shed further light on just how the dam failed.
The author has a bit of an axe to grind about how Los Angeles and its history is generally ignored by other parts of the country, despite it being one of America's biggest cities, but that only comes up in a few brief sections, thankfully. Overall, this was highly informative, and shed a lot of light on a somewhat obscure dam failure. While the majority of the information did eventually become relevant, there was a great deal more information than was really needed to understand the dam failure, and I feel like a bit more editing might have made this a bit more digestible, since most readers of a book about a dam failure are a bit more interested in the dam failure itself than the historical context. That historical context is valuable, but could have been a bit more streamlined than it was.