Book Paper and Book Cloth
Many types of paper or book cloth can be used in manufacturing, binding and repairing a book.

BOOK PAPER
Although many different types of papers are used to print and manufacture books, three important types of paper to be familiar with in book repair are uncoated paper, coated paper and acid-free paper.
Uncoated paper is the most common type of paper and is made from plant or tree fibers that are processed into sheets. Originally, most uncoated paper was handmade from linen or cotton rags. These older papers age very well because they contain few damaging chemicals.
In the 1860s, a process was developed to turn cellulose fiber from trees into paper. This type of paper can be made in large quantities but contains some very damaging chemicals that cause paper to become brittle more quickly than paper made from cotton or linen.
Coated paper – A sheet of paper can be impregnated with very fine clay to produce a very fine printing surface. Introduced at the end of the 19th century, coated paper is ideal for printing halftone illustrations. Unfortunately it is not very strong and is highly susceptible to water damage. Often the text pages of a book are printed on uncoated paper while the pages that contain illustrations are printed on coated paper. The coated paper may be part of the signature or tipped onto a page of uncoated paper.
Acid-free is a designation given to paper that has a pH value of 7.0 or greater on a scale of 1 to 14. Fibers from any source can be made into paper that is acid-free. Both coated and uncoated papers can be acid-free. The common types of acid-free paper used in book repair are photocopy paper and Japanese repair tissue.

BOOK CLOTH
Book cloth is a specially woven cloth backed with thin paper. The paper backing gives the cloth support, minimizes stretching and allows the material to maintain a crease.
There are three main categories of book cloth:-
Starch-filled book cloth in which the weave of the cloth is filled with starch. This type of cloth is sometimes called sized book cloth. Heavier book cloth is sometimes called buckram.
Acrylic, pryoxylin, or vinyl impregnated book cloth.
Plastic coated book cloth. 

Paper and book cloth have a grain just as fabric does and it is important to understand how that grain affects repairs. When the grain of the paper and book cloth runs parallel to the spine of the book, the cover and pages open freely and stay open without much effort. This is called “with the grain”.
Paper that is bound into a book with the grain running perpendicular to the spine of the book is called “against the grain”. Modern publishers often print the pages of a book against the grain to get more pages on a large sheet of paper. When the grain runs perpendicular to the spine of a book, the book can be difficult to open and it will not remain open without a great deal of pressure. Books printed against the grain are easily damaged since patrons must force the book open to read or photocopy it. When pages or the case of a book are repaired, the grain of the repair materials should always run parallel to the spine of the book.

These two posts should give you a better understanding of how a book is constructed so that when you begin your repair work you know exactly what parts you need to work on first.