What makes a book rare ?

Millions of books, pamphlets, magazines, newspapers, and broadsides have been published since the invention of printing more than 500 years ago. Only a small portion of these pieces, however, would be considered "rare" by specialists. In simple terms, books achieve a degree of rarity only when demand exceeds supply. Unfortunately, there are no easy formulas for determining rarity.

To know more about rare books :

http://rbms.info/yob.shtml

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