The first part of the book looks at the Phanerozoic eon - that is the Cambrian Period to the present, and tells mostly of the history of geology in Britain. The second part is more wide ranging, starting with the formation of the earth, and although it is based on a jorney into the Grand Canyon, in fact it takes a more global view.
I have to say that I struggled a bit reading this book. Since the thread of the first part is based on the geological divisions of time, the history aspect tended to jump about - it might go from the twentieth century back to the work of an eighteenth century scientist, and I found this confusing. When I started reading it looked as if it was going to be based on the journey of William Smith from London to North Wales, but this was only mentioned sporadically. It's a pity, since it would have helped to give a better thread to the book. As it is the book would be useful to those who have studied some geology - for instance those who have read several other books on the subject, for whom this book would help to pull the story together. However I would not recommend it for beginners.