I should probably disclose the fact that I haven't actually read this book myself (beyond a quick skim through), I bought this as a gift for my dad who is currently studying geology with the Open University. His praise for the book was so effusive, however, that I felt I should share his enthusiasm here! He thought the premise of the book was fantastic, to essentially tell the story of the earth's geology through a pebble, and he found the book thoroughly enjoyable and very informative. Obviously a book like this is not a substitute for a geology textbook, but that is part of it's strength - it is totally approachable for people with little background knowledge, without being too basic for people who have studied some geology.