Headband
The headband is a small strip of fabric or thread at the top of a hardcover book’s spine. It reinforces the binding and covers the signatures of the book block for a cleaner, more finished look. In high-end artbooks, the headband’s color can match the theme for a polished, stylish finish.
More on Headband and Tailband

A red arrow pointing to a white and black striped headband in an art book