mechanical forces (as opposed to the internal forces that arise from osmotic effects) become significant. Cats' Paws and Catapults is aimed at a broad general audience. There isn't an equation to be found in the text, but this doesn't mean that Vogel eschews either rigor or quantification; the relevant mechanics is throughly explained and its implications explored, with sufficient quanification that the similarities and differences between biological and human technology are explicit. The book is accessible to a bright and curious high school student and any undergraduate. The prose is often as elegant as D'Arcy Thompson's On Growth and Form but without the mysticism of the latter; this is hard science made easy, not watered down. (However, if you find puns distasteful, beware -- they pervade the book.) Unlike many popularizations, the text includes an excellent set of footnotes and a wonderfully eclectic and thorough set of references; those whose curiosity is piqued will not be frustrated by a lack of guidance for where to dig deeper. But Vogel's book is not just for a popular audience. The professional engineer will find here an introduction to the basics of natural selection, to the remarkable information paucity of biological systems (despite the information density of DNA), to the ubiquity of negative feedback systems at all levels of biological organization, to biological diversity and to biology's intriguingly different solutions to problems the engineer will find familiar. The professional biologist will find a painless introduction to the basic mechanics relevant to plants and