The language of genes has become common parlance. We know they make your eyes blue, your hair curly or your nose straight. The media tells us that our genes control the risk of cancer, heart disease, alcoholism or Alzheimer’s. The cost of DNA sequencing has plummeted from billions of pounds to a few hundred, and gene-based advances in medicine hold huge promise. So we’ve all heard of genes, but how do they actually work? There are 2.2 metres of DNA inside every one of your cells, encoding roughly 20,000 genes. These are the ‘recipes’ that tell our cells how to make the building blocks of life, along with myriad control switches ensuring they’re turned on and off at the right time and in the right place. But rather than a static string of genetic code, this is a dynamic, writhing biological library. Figuring out how it all works – how your genes build your body – is a major challenge for researchers around the world. And what they’re discovering is that far from genes being a fixed, deterministic blueprint, things are much more random and wobbly than anyone expected. Drawing on stories ranging from six toed cats and stickleback hips to Mickey Mouse mice and zombie genes – told by researchers working at the cutting edge of genetics – Kat Arney explores the mysteries in our genomes with clarity, flair and wit, creating a companion reader to the book of life itself.