The work gives a detailed analysis of the Reformation processes in Poland; it is centered mainly at the second half of the sixteenth century – for instance, at the religious and political circumstances of the reign of King Sigismund II and, particularly, at the sejms of 1552 and 1555. But in the first chapter, there is a description of the ecclesiastic situation by the beginning of the dissemination of the Reformation ideas; this survey is given for the sake of finding the reasons of the processes in question.

The work was based on various sources: not only already published Corpus reformatorum, but also non-published documents of Polish Protestant communities. The author put a special attention at the social and political character of the religious movement; particularly, he declares that the Reformation movement was a result of the struggle of local nobility and clergy, and because it was limited with noble circles, it could be called a movement of Szlachta.

The author also described contacts of local reformers with Calvin. Large parts of the work were on the so called Malopolskaya Church, Nontrinitarians, and the activity of Jan Łaski.

There are important conclusions on the reasons of the weak influence of Protestant ideas in Poland. On the opinion of L., the Reformation quickly went to its decline in Poland, because of the fact that Calvinists had no strong organization. The Protestant clergy was deprived from independence, the quantity of churches was insignificant – and the situation was worsened for them with regular shaping of new movements, for instance, with the separation of Nontrinitarians. Besides, the decline depended on the socially limited circle of participants of the Reformation in Poland – not all the states of the society were involved into the movement, so, it was rather superficial and lack of zealots.