What is a "wrap around jacket band"?
It is an obi, which is also known as

a strip of paper looped around a book or other product.

As Wikipedia continues to mention,

Many books in Japan are supplied with an obi, which is normally added outside any dust jacket. [...]
In English, the term belly-band is sometimes used instead.


The following image is the obi on Tokyo Ghoul:re volume 7.