My wife and I moved to Eureka CA in 2009, and soon thereafter I developed an almost insatiable thirst for knowledge about this "megathrust earthquake" that I learned was apparently imminent for our area. Somehow I had an image in my mind of waves 1000 feet tall and bits of the coast being broken off and submerged under the sea permanently. That's the movies; but this book is about the reality - tectonic plate theory, subduction zones, megathrust earthquakes, and the catastrophic tsunamis that result from these events.
It's written mostly as a history of the process of discovery that led scientists from an initial position of believing that the Pacific Northwest was completely aseismic (without earthquakes), through the various clues and slowly dawning realization that yes, in fact our region does have really big 9.0+ megathrust earthquakes (and corresponding tsunamis) every few hundred years. In fact, the majority of the book might be a little frustrating for someone who's just wanting to find out "what's gonna happen", because mostly it's a historical account of scientific discovery, interspersed with tales and descriptions of previous large earthquakes. Impatient people can skip to the last nine pages or so, where he outlines a frankly terrifying (though imaginary) scenario that entails what a 9.2 quake might do to the modern Pacific Northwest: Think along the lines of most of the tall buildings in cities like Portland and Seattle collapsing (since even the new ones are not built to survive 4 minutes or more of strong shaking on a frequency that makes these buildings vibrate like great big tuning forks), and a tsunami 30 to 100 feet high which will pretty much wipe out entire coastal communities.
So, are we doomed? No. It's not all about terror and calamity - one important point that gets made repeatedly is that history has shown that simple education and knowledge can keep you alive in situations like this. This book is not so much a tactical "how to survive" type disaster preparedness guide, as a strategic "big picture" view - why and how is all this happening. That said, sprinkled throughout the book are many tidbits of wisdom about these events that certainly served to fill out my understanding of how they unfold, and how to survive them.
If I was going to nitpick, then the biggest weakness of the book, really, is the fact that so much of it is taken up with the historical tale of how the scientists went from thinking there are no earthquakes here, to thinking that there are earthquakes (but not being too sure about whether there were lots of smaller ones, or just fewer really big ones), to finally discovering the clues that told them that Yes, this area does in fact get really, really big earthquakes occasionally. It is a fascinating scientific detective story, but all the talk about turbidites, ocean sea floor cores, ancient tree rings and underwater mudslides, while interesting, isn't riveting reading when you already know the final outcome. Yes, it is all fascinating stuff, and Yes, I really enjoyed reading it. I just wish the end part on what might happen had been fleshed out a bit more, because let's face it - that's what most people who buy this book want to know. The subtitle of the book is, after all, "The coming earthquake and tsunami that could devastate North America", which makes it sound like it's talking about what's GOING to happen here. But it could perhaps more accurately have been "The history of how we found out about Cascadia", because most of it is about the past. To have to wade all through that history, which ends up with nothing more than the simple realization that "Yes, we do get these big earthquakes and tsunamis" feels a little redundant, because we know this now, and the big questions are all about what's coming next - the future, how do we prepare, and what specifically can we do about it. But like I said, this would be nit-picking - for what it is, the book is a wealth of information. I would heartily recommend it to anyone who is remotely interested in Cascadia, in particular anyone at all who lives in the Pacific Northwest of the USA, this is for you - read it and learn.
Another slight nitpick is the lack of footnotes or references - sometimes he talks about "a study", without any note about the actual title or how to find it. There is a list of recommended reading at the back, but it's organized by year and there was at least one instance in the text of a referenced study from 2009, whereas there weren't even any entries under 2009 in the reading list. But again, this is a minor point - if you are interested at all in Cascadia's subduction zone, then this book is a must-have.
Finally, I hadn't realized before buying this book that the author was also behind the making of the CBC documentary "Shockwave". I recently got this on DVD (direct from the publishers, Omnifilm), and it's a very good companion to the book if you can get hold of it. It's something else to see on TV the experiment that he describes, where they built a scale model of Seaside, Oregon in a wave tank and then film a scale tsunami wave as it overruns the town. Sobering stuff indeed.