To customize printing books, here are some several common forms of hardcover books for you :
Divided by the form of the spine, there are two types:
1. The square spine of perfect binding book is thicker than the book block. Due to the folding and stringing of the book block, the height of the spine is higher than the book block, and the more printed sheets, the more obvious. Therefore, hardcover books with square spine should not be too thick, and generally suitable for spine within 20mm.