Ju refers to juvenile so what does this mean about a book?

"Ju" in the context of a book likely refers to juvenile, meaning the book is intended for young readers.

Here's why:

* Juvenile literature is a broad term encompassing books written for children and young adults, typically ranging from picture books to young adult novels.

* The term "ju" is a shortened, informal way of referring to juvenile literature, especially in library and bookstore contexts.

So, if a book is described as "ju", it signifies that it's aimed at a younger audience.