This monograph by Natalia Nowakowska fills an important gap in the research on the Reformation in Poland. This excellent study will serve as a credible interpretation and a handbook not only for students, but also for the broader public. The book not only describes the development of the Reformation, but also offers a profound and analytical study that addresses the attitude of political and intellectual elites in Poland toward the Lutheran movement. The main question of the study concerns the degree of tolerance seen in the stance of the Polish monarch, who apparently acted paradoxically. On the one hand, he published eleven edicts against the Protestants and conducted a military intervention in Gdańsk, where he sentenced over a dozen alleged Protestants to death. On the other hand, not only did he explicitly refuse to prosecute heretics, but he also allowed Albrecht Hohenzollern to convert to Lutheranism and, over the years, protected the Duke of Prussia against the emperor and the pope. Nowakowska claims that the answer to this riddle lies not in political calculation or in opportunism, but in “pre-confessional ecclesiology” (18, 219). According to the author, the Polish king and the Catholic elites were willing to tolerate some Lutherans because they still perceived them as a part of the Catholic world.

After an introduction where she discusses the current state of research on the topic, her main thesis, and her methods, Nowakowska provides, in the second part, a framework for the upcoming analytical chapters. In the sections that follow, the author looks at different aspects of the history of the Reformation in Poland: the development of the movement in the cities of Royal Prussia, the relationship between the Polish monarch and the Lutheran Duke of Prussia, royal edicts against the Reformation, the place of the Reformation in the international diplomacy of the Polish court, and the attitude of the Polish church toward Lutheranism. In the book's final section, Nowakowska changes the topic and analyzes the language used to define the new teaching and to defend the Catholic Church. Whereas the first three parts of the book summarize the state of the research in a brilliant way, the fourth presents a new perspective on the Reformation.

Despite the title, which suggests that the chronological frames of the work coincide with the reign of Sigismund I (1506–48) or with the development of the Reformation during his reign, the monograph deals only with the years 1518–35. The author explains the closing date with “the passing of an entire generation of counsellors” (14). However, in 1535, only one main politician from the king's circle had died: Piotr Tomicki, the vice-chancellor and bishop of Kraków. The decision to end the period researched in 1535 seems to be rather pragmatic (45): the largest group of sources used by Nowakowska were the Acta Tomiciana—a collection of documents relating to the career of Tomicki, prepared by his secretary, Stanisław Górski (1497–1572), and edited in the twentieth century. Besides this printed collection, Nowakowska uses a variety of handwritten sources from church archives in Gniezno, Kraków, Olsztyn, Poznań, Włocławek, and Rome, but they have only a secondary role in her argument. An important handwritten source used by the author is a manuscript from the nineteenth century, stored in the Jagiellonian Library (MS 5357, written in the bibliography mistakenly as 5337, but correctly in appendix 1) and consisting of copies of various ecclesiastical court records from the sixteenth century. Some of the originals that served for producing the copies are stored in the Archives of the Kraków Cathedral Chapter (Archiwum Krakowskiej Kapituły Katedralnej), which was not consulted by the author.

The analysis of the king's policies is thoughtful; nevertheless, it provokes some questions. If “the Reformation in Sigismund I's Polish monarchy was … not theologically homogenous” (194), then why does the author follow the style of the Catholic sources and label all the Protestants as “Lutherans”? Some corrections are needed to the reconstruction of the events in the cities and the politics of the king, where the author uncritically repeats claims of previous research. For example, she repeats a story about Jakub Knade, who, she claims, started preaching in Gdańsk in 1518 (49), although the date is too early. In 1526, the Polish king sentenced to death not thirteen (11, 57, 119, 218) but fourteen Protestants. The Sejm in 1529 gathered not in Sandomierz (101) but in Piotrków. Between 1526 and 1534 there was no “hiatus of seven years” without anti-Protestant edicts (122) because it is known that the king published or reinforced his earlier decrees in 1527, 1528, and 1533. Some minor mistakes are found in the spelling of German, Polish, and Latin names and titles.