The austere buildings of the Bossche School are all about the spatial effect of the architecture. These were the years of reconstruction when new churches, homes and town halls were built using inexpensive materials. The architects of the Bossche School applied the theory of proportion developed by Dom Hans van der Laan, the "Plastic Number." However, Van der Laan himself did not design and realize many buildings. Jan de Jong is the most prolific architect of this Bossche School. The second part of the monograph focuses on how Jan de Jong applied the Plastic Number. For this purpose, the authors analyzed a large number of key works from the architect's oeuvre. This voyage of discovery begins with his entry for the competition for the Pelgrims Church in Syracuse (Italy) from 1956 - 57 and takes us past churches in Gemert (1955 - 59), Rijswijk (1956 - 59) and Eindhoven (1961 - 64), the Prorij Emmaeus monastery in Maarssen (1958 - 66) and the architect's home in Schaijk (1956 - 82), among others. There is a difference in the approach to the Plastic Number by theorist Dom van der Laan and how Jan de Jong applied it in practice. Moreover, the ideas of both Jan de Jong and Van der Laan developed in different directions over time. For example, Jan de Jong did not work with the morphotheque developed by Dom van der Laan, a block box of shapes according to the proportions of the Plastic Number. In addition, there is a big difference in the approach to the urban planning situation, in which Dom van der Laan's theory initially offered no solution. Later, Van der Laan developed a somewhat rigid theory to fill this gap. This theory is nothing like how carefully Jan de Jong fitted his projects into existing situations. There are many examples of this in the book. See for example the church in Rijswijk where the outbuildings provide a transition between the surroundings and the church or the housing project on the Gasthuisstraat (1975) in Grave that follows the existing street pattern. If you want to know more about the theory that Jan de Jong himself developed for urban planning, this can be found in the first part of the monograph. In part two the application of the 'Plastic Number' is discussed in detail for the first time on the basis of realized work. To this end, the book is enriched with many mathematical examples and drawings showing the use of the Plastic Number. However, those who want to understand these analyses will first have to read the explanations at the back of the book. The book concludes with a richly illustrated survey of works.