I enjoyed so much Dava Sobel's previous books, "Longitude" and "Galileo's Daughter" (both of which were Hal's Picks), that I was eager to read her latest, which was judged "best science book" for Fall, 2011 by Publisher's Weekly. I have read a lot about Copernicus lately, including both Owen Gingerich's "The Book Nobody Read" and his article about Kepler and Brahe in the September, 2011 Physics Today. Despite knowing something about Copernicus' science, the man himself was a cipher to me - one that Sobel has turned into flesh and blood. It is not easy to research the private life of an individual who lived five hundred years ago, even if that person became famous. Sobel's task was facilitated considerably by the fact that Nicolaus Copernicus was not only a scientist but also a canon in the Catholic Church, and so records related to his ecclesiastical duties supplement a scanty scientific history. Sobel has a theory - that Copernicus postponed publication of De revolutionibus orbium coelestium until near the end of his life because he feared that it would further the cause of the Lutherans. She invents a dialogue between the aging Copernicus and Georg Joachim Rheticus, a young Lutheran mathematician who encouraged and aided the older man in publishing possibly the most important scientific treatise in the history of the world. The invented dialogue is boldly inserted as two-act play, around which the factual history of Copernicus becomes the bread of this sandwich. The fact/fiction separation is manifestly clear and the intellectual and religious controversies are beautifully elaborated.