This book is about molecular nanotechnology for the layperson. According to the glossary of the book, molecular nanotechnology is “thorough, inexpensive control of the structure of matter based on molecule-by-molecule control of products and byproducts; the products and processes of molecular manufacturing, including molecular machinery.” Basically, what if you could build something by assembling it one molecule at a time? The book covers the technology itself, paths leading to the development of the technology, and the positive and negative social and economic consequences of the technology. This is a fascinating subject, but I found the book tedious to read. I think this is due in large part to the numerous “scenarios” that the authors present. There are two main problems with the scenarios. First, the book dwells too much on the fact that they are scenarios. Second, the scenarios are too explanatory to be good stories, and too tedious to be good explanations. Perhaps science fiction would have been a more effective format. Additionally, I believe this book paints an overoptimistic picture, for two reasons. First, I feel that the scientific and engineering difficulties in developing nanotechnology have been glossed over. For example, it is one thing to note that plants can transform sunlight into stored energy; it is another to suggest, with no justification or explanation, that we can engineer an equivalent system. Second, despite the authors’ claim that this is not an optimistic book, I think the difficulties in preventing accidents and abuse have been underestimated. For those of you familiar with SETI and the Drake Equation, perhaps the true measure of L, the lifetime of communicating civilizations, is not the ability to survive nuclear weapons (which seems to be the commonly assumed limiting factor) but the ability to survive nanotechnology.