The process to provide a strong covering holding the pages of a book together is called binding.
File Format For Binding
(in an event of 2 continuous pages meeting together, additional cutting may apply)
It uses glue to bind the pages and cover together, in the process of book binding, the binding side (which is the spine) will be cut and glue will be applied prior to attaching the book cover.
Generally, this method does not allow full expansion of pages, hence, a margin of 13mm should be left without any important information as pages are unable to expand fully to display information within the margin.
If the inner paper used for your book is too thick, the binding side might crack when the page is open.
Saddle stitching allow complete unfold of pages.
The total cover and inner pages must be in the multiple number of 4.
Ring binding allow complete unfold and flipping of pages.
Please ensure not to include any important information 15mm inward of the binding surface.