Hard cover books are casebound, the case being the hard covering that is attached to the book.
There are so many ways to casebind a book that it just won’t be possible to describe each variant of the process.
Briefly, a set of F&G’s is bound as a book block. The binding can be as inexpensive as a thin layer of adhesive glue binding the pages to a thin strip of cloth or paper. On the other extreme, the F&Gs can be tightly sewn (generally Smyth sewn) with thread through the spines of each signature. Sewing is the historic and traditional method producing a strong binding that can be opened and closed frequently.
Years ago the threads that were hanging out of the sewn book were ornately tied off and became known as headbands. Today decorative strips of colorful woven thread can be glued onto the head and foot of the spine before binding. They are nonfunctional but inexpensive decoarations available in a variety of colorful combinations.
End sheets (or endpapers) are sheets twice as wide but the same height as the book’s pages. They are folded to the book’s page size and glued along to the front and back page with a thin application of white glue. While there are many ways to cut corners here, there are also many ways to decorate. Endsheets can be special order paper, even handmade as long as it is sufficiently strong to support the text in the case. The minimum weight would be around an 80# text although many current books settle for something less, allowing the text to rip out of the case.
The inside covers of the case get an application of glue and the book block is set into the case and clamped so the endsheets firmly secure to the inside covers. To further strengthen the bind, a strip of cloth can be glued to the inside cover and the spine behind the endsheet. This is called a reinforced endsheet and is highly recommended for books that will be in frequent service (ie hymnals, textbooks) and books printed on heavy paper or high page counts.
While the text of the book has been preparing for the case, the case is being made.
The case is made of two binder boards (think stable chipboard) with a covering glued to them. The covering can be as expensive as leather or buckram or as cheap as text paper. The cover can be preprinted on cloth or paper, or embossed or foil stamped. It can be a single piece of covering that extends around the spine and over the binder boards or it can have a different covering over the spine (a three piece case).
The thickness of the binder boards is described in decimal format with standard thicknesses of .080, .088 (very common), and .098. Your designer may be able to suggest an appropriate thickness because it’s not necessarily a matter of more is better.
The covering material is glued to the boards, the edges and corners “turned in” and the case is ready for the trimmed book block.