It looks like two column, but the column size of left and right is not same. The smaller column is on the left if the page number is even, it is on the right if the page number is odd. The smaller column is used to place figures and tables. Also, the header is placed at the top of the smaller column, and its style is not default.
How to make this layout?

tufte-bookclass. More info in this example. – Fran Aug 28 '17 at 20:05