Most paper today is bleached and contains acid. It is not intended to last for centuries, and will deteriorate when exposed to damp conditions or bright sunlight. Acid free paper, while more expensive, is far more durable.
Many cheap books are bound by gluing the individual pages to the binding spine. These books will not last. In order to be durable, the pages have to be doubled over in bundles known as "signatures," then stitched onto the binding with strong thread.
Glue serves a number of purposes within a book binding. It holds the endpapers to the front and back cover, which helps to hold the text block inside the binding. In many cases it takes the place of stitching at the spine.
The distinctive raised bands that are found on the spines of older books are not merely decorative. These are the strong cords that attach the text block to the binding. This is the best method, and is the reason that many very old books are still in one piece.
Paper can be made from a multitude of materials, including linen, hemp and wood. Bindings are made from such materials as paper, cardboard, buckram and leather.