This book is simply a magnificent account of the Earth's structure and how it "works". Taking as his framework a series of visits to key sites - including Hawaii, Vesuvius, the Alps, Newfoundland and the North West coast of Scotland - Fortey explains not only the structure of the Earth and how it came to be as it is, but also how our understanding of that structure has grown and developed over the past 2000 years. He also finds space to fit in (relevant) musings on the nature of progress in science, ecology and the effect of humans on the environment, and much more. A recurring theme is the effect of the underlying geology on the visible land and the way it is used. (In passing, I think this book would make excellent television.)
The book concludes with a virtual tour of the globe, swooping down to comment on this feature or that aspect, unifying the earlier, more particular studies in a spectacular fashion.
Fortey's writing is beautiful and well worth reading for its own sake, and his explanations are excellent. There are relatively few illustrations and diagrams, and more of these might have helped, but this is a very slight flaw in a wonderful book.