"En vaste burg is our God" is a book in which the author Betsy de Heer commemorates the fourth centenary of the Reformation, which was celebrated in the period from 1517 to October 31, 1917. This work examines the important events and principles of the Reformation, the influence of which is felt even in our time. The author examines the role of the church in the process of reformation, its heritage and significance for modern society. Readers will gain a better understanding of the historical context and spiritual values that underpinned the Reformation through this engaging book.