The book “Desseins de toutes les parties de l’eglise de Saint Pierre de Rome only has a few pages filled with text. Mostly it is composed by architectural drawings and plans. All the text is handwritten, and the layout is kept quite simple. The pages with only text on them have big headings and are framed with a thick black line. Because most of the text are letters or agreements, sometimes there are signatures on the bottom of the page. The pages with the drawings and plans, only have text in form of captions. The layout of them is really simple.
All drawings are architectural drawings. The intention of the author was to give an insight on how the building looks, not on how it is built. That’s why the drawings do not contain any technical elements as measurements or construction details. The drawings show overviews as well as really detailed drawings.
The images (drawings) nearly always fill the whole page. They are the important part of the book and fill almost every page of the book, leaving every second page blank to protect the prints. They were glued in later and they are not numbered nor referenced but organized in a way that the further in the book, the more detailed the drawings get.
The book documents the work of an architect on behalf of the king. So the book was supposed to transport information and document an important building. Now it can be used as a reference and documentation.