Some of the best popular science books tell us as much about the people as the science, and that is the approach taken byDaniel Davis. In exploring the ‘compatibility gene’ (or more accurately, the ‘compatibility genes’ – I don’t know why it’s singular in the title). He takes us on a voyage of discovery through the key steps to identifying the small group of genes that seem to contribute to making that individual more or less compatible with other people, whether on the level of transplants or sexual compatibility, taking in our growing understanding of the immune system along the way. It probably helps that Davis is a practising scientist in the field – the director of research at the University of Manchester’s Collaborative Centre for Inflammation Research and a visiting professor at Imperial College, London. Often, frankly, discovering the book is by a working scientist can mean turgid text or an inability to explain the science in a way the general reader can understand, but Davi...