The bestselling - and hugely timely - guide to the science of contagion, revised and updated to address topical content: sheds light on the COVID-19 pandemic as well as gun violence in America, the spread of fake news, social media and its effect on our mental health. Explores complex mathematical ideas in a straightforward way, and is full of human anecdotes - from friendship circles to gun violence and dangerous rumours. A TED fellow, the author's online talks have been viewed over a million times.