In Compass, Alan Gurney reconstructs the long, staged evolution of the compass: from the first magnetic needles to modern navigation technology. He explains how early navigators relied solely on sight and wind, and how the invention of magnetic navigation enabled safe ocean crossings, accurate map usage, and global exploration. The book details technical and scientific challenges, including magnetic variation and dip, compass deviation caused by ship metal, efforts to improve compasses, the development of dry versus wet compasses, and later innovations such as gyrocompasses. Gurney also highlights the human side: stories of sailors, shipwrecks, explorers, and inventors, showing how navigational errors could be catastrophic, and how compass development influenced the course of history. The book includes maps, illustrations, and historical documentation, making it a combination of history of science, maritime history, and cultural history