A few frequently used words to describe a rare book:

Fore-edge:
The fore-edge of a book is opposite the spine, where the pages open. 

Boards:
Stiff covers, usually made of cardboard or wood, that form the front and back of a book. Boards are covered with cloth, leather, paper, and other types of material, and provide structural support and protection to the text block.

Spine:
The part of the book where all the pages are held together; it runs vertically along one side of the book and is visible when the book is shelved upright. The spine often bears the title, author’s name, and publisher’s imprint.

Joints:
The hinges or flexible areas along either side of the spine where the boards meet the spine. The joints allow the covers to open and close smoothly without damaging the binding.

Raised bands:
Horizontal ridges or bands visible across the spine of a book. Traditionally, these bands are formed by sewing supports beneath the covering material, though they may also be decorative on modern bindings.

See also our article Different types of bindings