Provided is a booklet including: a plurality of leaves 2; a spine 4 that couples bound edges of the leaves 2 via a flexible glue layer 3; and a front cover 5 and a back cover 6 each having at least an entire area of a surface portion continuing to an entire area of a surface portion of the spine 4, wherein a flexural strength of the spine 4 backed by the glue layer 3 is set such that the spine 4 is flexibly deformed inwardly at a near acute angle together with the bound edges of the leaves 2 when center pages of the leaves 2 are spread.
