noun
folding book; accordion-folded book
A book made by folding a long sheet of paper back and forth, often used for picture books, sutras, or pamphlets. Also refers to the folded sections themselves.
この絵本は折り本になっていて、広げると一枚の長い絵になります。
This picture book is a folding book; when you open it up, it becomes one long picture.
経典は折り本の形で保存されて
Sutras are often preserved in the form of folding books.
Compound of 折り (ori, 'folding') + 本 (hon, 'book'). The exact historical origin of the format is uncertain, but it has been used for centuries in East Asian bookmaking.