The authors' theme is that we each react to and are changed by our environment which in turn reacts to and is changed by each of us. In the end, one can design computers only within a particular consensual domain that entails at least some commonly understood rules and concepts. The authors rely heavily on the philosophical works of Maturana and Heidegger. Difficult to read as some word meanings are developed through usage and demonstration (e.g., "throwness"). Also, quotes from references are used endlessly to substantiate their theme. This is nice but I wonder after all is done, what contributions the authors' have made and how much is simply a rehash.