Not all viruses are out to get us - in fact, the viruses that do us harm are vastly outnumbered by viruses that can actually save lives. At every moment, within your body and all around you, trillions of microscopic combatants are fighting an invisible war. Countless times per second, 'good' viruses known as phages are infecting and destroying bacteria. These phages are the most abundant life form on the planet and have an incredible power to heal rather than harm. So why have most of us never even heard of them? The Good Virus reveals how personalities, power and politics have repeatedly crashed together to hinder our understanding of these weird and wonderful life forms. We explore why Stalin's Soviet Union embraced using phages to fight disease but the rest of the world shunned the idea. We find out why scientists only recently realised phages are central to all ecosystems on Earth. And we meet the often eccentric phage heroes who have shaped the strange history of this field and are unlocking its exciting future. Faced with the threat of antibiotic-resistance, we need phages now more than ever. The Good Virus celebrates what phages could do for us and our planet if they are at last given the attention they deserve.