In this timely and well-documented book, Holland (Univ. of York, UK) provides careful, nuanced analyses of the key concepts and main arguments for and against the need for more stringent legislation with respect to the vast quantities of health-related information gathered from individuals today, amounting to an "ocean of datafication." In seven chapters addressing such topics as harm, privacy, anonymity, identifiable data, and consent, Holland argues convincingly that in most cases potential harms are seriously overstated, while the resources available to protect sensitive data are understated. Such debates crucially involve the appropriate use of Mill’s harm principle, according to which it is justifiable to infringe on personal liberty if the harm to society of not doing so will be significant. Many authors claim that more control is needed to protect the privacy of individuals whose data is collected through research. Yet Holland advances the view that progress in disease control depends on exploitation and analysis of such big data. Too much legislation risks reducing scientists' ability to conduct valuable public research and find solutions to intractable problems. Holland has authored highly regarded medical ethics texts, for example Bioethics (2nd ed. CH, Jun'17, 54-4750), and guides research governance within the UK public health establishment. Summing Up: Recommended. Upper-division undergraduates through faculty and professionals.