'This book is not just about life, but about discovery itself. It is about error and hubris, but also about wonder and the reach of science. And it is bookended with the ultimate question: How do we define the thing that defines us?' - Siddhartha Mukherjee, author of The Gene

We all assume we know what life is, but the more scientists learn about the living world - from protocells to brains, from zygotes to pandemic viruses - the harder they find it to locate the edges of life, where it begins and ends. What exactly does it mean to be alive? Is a virus...