The notebook has shaped the world for eight hundred years. In medieval Italy, the blank ledger transformed international trade, and enabled the intellectual artistic advances of the Renaissance. At sea, the invention of the logbook expanded horizons on the journeys of Magellan and fellow discoverers. Artists from Leonardo da Vinci to Pablo Picasso, thinkers from Isaac Newton to Albert Einstein, writers from Chaucer to Henry James: all created work forged in their notebooks. Roland Allen follows a trail of ideas, revealing how the notebook came to be our most durable tool for thinking. He tells the stories of its development through table-books and diaries, common-placing and journaling, and the lives of those who relied upon it: from Darwin hatching the idea of evolution to Clara Nguyen creating a restaurant business from family recipe books.