If the book in question is a significant contribution to human knowledge or life, such as a first edition (the first publishing of the book), or is locally significant to a specific place or site, it can be considered important and eligible for conservation. If the book would be difficult to replace, even if its market price is cheap, the book is rare, and thus of high importance.
A book is scarce if there are a limited number of copies available in print, either because few copies were initially printed or because copies have been lost over the years. Any book printed in a quantity of less than 500 is potentially rare. Some books, such as limited editions or those signed by the author, are published as instant rare books.
Brinkley, Frank. Japan : Described and Illustrated by the Japanese. Mikado ed. Vol. 1., Boston: J. B. Millet Company, 1897.
Special Collections (Oversize) DS809 .J37
A book's rarity due to age ranges from any book published before 1900, especially on the Americas, to those not more than 20 years old, thus it is important to combine these factors with those previously mentioned.
The imprint--the publisher and place and date of publication--helps determine a book's value. Most commonly, the later the place of publication was settled and the earlier the date of publication, the more valuable the book.
Condition assesses a book's damage and wear upon retrieval, looking into the binding, pages, book completion, and any markings the book may have. This damage, including non-original binding, brittle or damaged pages, and missing pages or illustrations, detracts from the market value of a book but not necessarily from its informational value.
Specific parts of a book's appearance can add to its value, such as handmade bindings, bookbinders' signatures, original photographs, color plates, or fine illustrations. One of the most valuable physical properties a book can have is a fore-edge painting--a picture done by hand on the page opposite the spine of a closed book. Books with any of these properties are likely to be carefully protected in the archives.
If a book is connected to a notable owner, it will have significantly more value than any other book of its kind. This value increases if the famous owner signed it, affixed their own bookplate to it, or made notes in it.
Hurston, Zora Neale. Dust Tracks on a Road : an Autobiography. First edition. Philadelphia: J.B. Lippincott Company, 1942. Signed by Maya Angelou.
Special Collections (Rare Books) PS3515.U789 Z5 1942
Subject matter is not necessarily a crucial factor in a book's value, but collectors like museums and historic sites may look for books relating to their topic of study or location. If there are few of those, the books become rarer, combining the factors of subject and scarcity.