If you are interested in what Copernicus did, save your money and time and don't buy this book. Instead, get ahold of Thomas Kuhn's masterful account "The Copernican Revolution".
This book is one of a series in which non-scientists present popular accounts of mostly great episodes in science. I say mostly great because there seems to be a certain amount of political correctness in the choice of scientists to write about in the series. But I digress.
Some of the books in this series are successful, for example the one by Madison Smartt Bell on Priestley, Lavoisier, and the chemical revolution. But when you have fiction writers expounding technical subjects, there is potential for trouble, and that is what we get with Vollmann's book on Copernicus.
Vollmann's explanations of the technical aspects of Copernicus' work are superficial and hard to grasp. Kuhn is much better. Vollmann also has a complusion to say snotty things about everyone involved, about their thoughts, motives, habits of mind. One would think that the ancients who constructed early science and astronomy were a bunch of idiots who had to wait for Copernicus to come along, who of course was a dolt because he was "obedient" to Aristotle for the most part, and was incapable of writing clearly to boot. Kuhn is incomparably better at explaining the philsophical, religious, scientific, and historical contexts in which the ancients, Copernicus, and the other early moderns worked. For example, you get a real sense of why the ancient earth-centered system was the reasonable system, that the ancient heliocentric precursors of Copernicus didn't have much in the way of evidence or reason on their side. You get a sense from Kuhn of just what it was that made the heliocentric theory attractive to Copernicus -- the changing context of observational astronomy, and above all the clarity which the heliocentric view gave to the matter of the oddities of the motion of certain of the planets.
If you really want a sense of the greatness of ancient scientific thought, of ancient astronomy, of the magnificence of the accomplishment of Copernicus and his followers in the modern scientific revolution, get ahold of Kuhn's book.