Copernicus writes of the heliocentric theory of the sun. A theory that eventually came to be accepted as fact even throughout all of the controversy. Published on his deathbed, Copernicus never got to see the results of the can of worms he opened.

In any case, there is no real prose, and most of the book is dense mathematical proofs and theorems developed from Euclid's Elements. It really hasn't aged well, but Copernicus and astronomers in general kept fantastic records of calendar dates. The reason it hasn't aged well is because of the methods of proof utilized. All of them are proved using diagrams and pure geometry. They don't even have modern terms for mathematical operations yet, so instead of equals and whatnot, you get something like "additosubtraction."

All in all it is a very fascinating read if you are the type of person that would go for this kind of subject. Beyond that, it is really quite dry and mathematical. ( )

Facsimile of Kepler's copy, with his marginalia

[On the Revolution of the Heavenly spheres, ] Nicolaus Copernicus.
I did not actually read On the Revolution of the Heavenly spheres in its entirety, because the mathematics would have been way beyond my comprehension, but I did find something called Copernicus Work book edited by Patrick Bruskiewitch which contains a large extract from book one of "On the Revolution of the Spheres" as well as Copernicus "A Commentary on the Hypothesis concerning celestial motion" The work book contains an article which introduces Ptolemy's "Almagest" and the concept of the spheres. It also takes the story further with how the study of astronomy developed after the death of Copernicus over 70 years later with Tycho Brae and Galileo's telescope.

Book one of On the Revolution of the Heavenly spheres is perfectly readable and for me added some details that fleshed out my previous understanding of early astronomy. The headings of the sections will give a good idea of the content:

Preface to the revolutionibus with a dedication to the most Holy Lord Pope Paul III;
That the universe is spherical
That the earth is also spherical
How Earth with the water on it forms one sphere
That the motion of the Heavenly bodies is uniform, circular and perpetual or composed of circular motion
Whether circular motion belongs to the earth and concerning its position
Of the vastness of the heavens compared with the size of the earth
Why the ancients believed the earth is at rest like a Centre in the middle of the Universe
The insufficiency of theses arguments and their refutation
Whether more than one motion can be attributed to the earth and of the centre of the universe
Of the Order of the Heavenly bodies
Explanation of the threefold motion of the earth

For anybody who may be interested in the workbook here is the link https://archive.org/stream/CopernicusWorkBook/Copernicus_Book#page/n41/mode/2up ( )

This remarkable work stands as one of the supreme monuments of science. It profoundly influenced, among others, Galileo and Sir Isaac Newton.