I just finished this book recently - it's a brief but fun exploration of some fascinating biological questions. Each short chapter begins by defining a question (Why is the Earth Green? Why is the Sea Blue? When Will the Biosphere End? are some examples) and then discussing some possible answers from the scientific literature. The authors typically give some succinct background information and then provide what appears to be a very balanced, thoughtful analysis of the issues and possible answers to these complex questions. Although some of the discussion gets fairly technical and I glossed over a few parts of some chapters, the overall style and approach is quite readable and I think that most well educated folks would get a lot out of this book. I highly recommend this book!