I have no idea how the first person got thought to create book in this shape. What I can say to that person is “well-done”. If you look through the publishing history, you might notice that they did not change much from the past.
Not only change so little, but the shape of its has been used and adapt into many things. Such as collecting bag in the picture.
Yeah, it looks vintage, warm and cool in the same time. Cannot resist to look at it right?