At the age of 36, on the verge of a completing a decade's worth of training as a neurosurgeon, Paul Kalanithi's health began to falter. He started losing weight and was wracked by waves of excruciating back pain. A CT scan confirmed what Paul, deep down, had suspected: he had stage four lung cancer, widely disseminated. One day, he was a doctor making a living treating the dying, and the next, he was a patient struggling to live. With incredible literary quality, philosophical acuity, and medical authority, he approaches the questions raised by facing mortality from the dual perspective of the neurosurgeon who spent a decade meeting patients in the twilight between life and death, and the terminally ill patient who suddenly found himself living in that liminality.