The book as a whole descibes 50 different kind of doors. In those 5 pages he describes 30 methods to build a door in a rustic way.
The first page is the only one that differs apart from the other ones. But this differentiation is only because of the title.
Every page is structured by the sub-chapters on it. And as every sub-chapter is different the sites vary a bit while still appear to be connected.
We can also see that he begins immediately with the first door, leaving any sort of introduction.
Every chapter starts the same in a formal point of view as the first sentence is always outdenting slightly.