This book was most likely printed with some sort of a press, using a single plate for each page. It is possible that these plates weren’t always aligned perfectly – which I suspect to be quiet hard. The result is of this can be seen on the page below. In contrast to this page, the two-sided page is really impressing, as the plates have to perfectly aligned!
I also found quiet interesting, that both pages leave a lot of blank space next to the drawing / the text – I guess its just space for personal notes for the owner of the book.