During the 1530s, rumours of a potentially revolutionary theory of how the heavens worked emanating from a small city in Poland began to spread throughout Europe. The architect of this theory was a Polish cleric named Nicolaus Copernicus. In around 1514 Copernicus had written and hand-copied an initial outline of his heliocentric theory, in which he placed the Sun, not the Earth, at the centre of our universe, with the planets, including the Earth, revolving about it. Titled his Commentariolus, it circulated among a very few astronomers. Over the next two decades Copernicus expanded his theory through hundreds of sightings, leading to a secretive manuscript whose existence tantalised mathematicians and scientists all over the world. In 1539 a young German mathematician, Georg Joachim Rheticus, travelled to Frombork to meet Copernicus; months later he departed with the manuscript for the book that would change the way we understand our place in the universe. Rheticus arranged for the publication of De Revolutionibus Orbium Coelestium (On the Revolutions of the Celestial Spheres) - legend has it Copernicus received a copy on his deathbed.This book would forever change the way we thought about our place in the universe. In her compelling style, Dava Sobel chronicles the history of the Copernican Revolution, relating the story of astronomy from Aristotle to the Middle Ages. And as she achieved with her international bestsellers Longitude and Galileo's Daughter, in A More Perfect Heaven, Sobel expands the bounds of popular science writing, giving us an unforgettable portrait of a major step forward in the human knowledge of our universe.