Yes, as a few other reviewers have noted, this book is written in a rather eccentric style. That, however, was only a problem for me when I went looking for things I'd read and discovered the table of contents made no sense.
On the other hand, the writing is conversational and detailed, thorough and startling. This is one of those books "everybody should read," because the information in it - particularly in the last third - is so incredibly critical to the fate and future of the human race.
Calvin has done one of the best jobs I've seen of explaining how and why the Atlantic currents transport heat and salt - and what happens when they shut down, plunging the entire world into an ice age in as little as 3 to 12 years. (This isn't a just a future threat - it's also an observation of times past. Every ice age has started and ended in fewer than a dozen years!)
Calvin tells us in detail how Europe will be devastated by the next ice age, how our SUV usage today in North America is leading us right to it (and much sooner than most think), and - most amazingly - offers some specific suggestions about things that can be done to stop it (like daming up some fjiords in Greenland and dynamiting others).
Along the way, we also get a completely new view of human evolution, based in the whiplash environment humans survived for the past 200,000 years.
This book is brilliant, and I highly recommend it. Just be sure to mark up the pages as you read them, because that's the only way you'll be able to find things later when you try to explain it to your friends (as you will want to do!).