The spine of a book is the part that connects the front and back covers, typically running along the side of the book. It serves as the anchor for the pages and holds them together, giving the book its shape and enabling it to stand upright when placed on a shelf. The spine usually displays the title, author’s name, and publisher's logo. In children's books, the design of the spine can be particularly important, as it's often colorful and engaging, helping to attract young readers and make the book appealing on shelves.