the shape of a book is

A triangle would be an interesting novelty for something like a children's book, but imagine how inefficient the blocks of text would have to be, how much more time they would take to create and such. This would not be practical for more than a single fun idea. Ditto for a hexagon, octagon, etc. What about a circle? Same space problem, plus, there would be no easy way to bind it.

the shape of book is box or long square