This novel, important, clearly written book brings together several familiar subjects whose connections had not been appreciated. We are grateful for widespread electric lighting (a relatively new phenomenon in human history), and we fear widespread breast cancer and prostate cancer. Many of us have also heard of biological clocks and the hormone melatonin. The authors assemble evidence that the blessings of electric lighting are a risk factor for the curses of breast cancer and prostate cancer, mediated by effects on our biological clocks and our melatonin production. Hence this book will interest not only scholars but also the broad public. Jared Diamond Professor of Physiology, Environmental Health Sciences, and Geography at the University of California, Los Angeles