I chose the first spread because of the very elaborate decorations on both pages. These decorative elements can only be found on very few pages throughout the book and seem to act as dividers between the different parts of the book.
The second spread showcases the structure of the first main part of the book. First comes a figure number and then the accompanying text. The text length varies between the figures.
The structure of the second main part gets shown in my third spread. The pages have a bigger format then the rest of the book and have to be folded to fit in. The drawings most likely correspond to the figures and text in the part before.