A celebrated mountaineer and author searches for meaning in great adventures and explorations, past and present. David Roberts, "veteran mountain climber and chronicler of adventures" (Washington Post), has spent his career documenting voyages to the most extreme landscapes on earth. In Limits of the Known, he reflects on humanity's-and his own-relationship to extreme risk. Part memoir and part history, this book tries to make sense of why so many have committed their lives to the desperate pursuit of adventure. In the wake of his diagnosis with throat cancer, Roberts seeks answers with sharp new urgency.