Bibliog'raphy, the knowledge of books, in reference to the subjects discussed in them, their different degrees of rarity, reputed and real value, the materials of which they are composed and the rank which they ought to hold in the classification of a library. The subject is sometimes divided into general, national and special bibliography, according as it deals with books in general, with those of a particular country or with those on special subjects or of a special character, as early printed books or anonymous books. A subdivision of each of these may be made into material and literary, according as books are viewed in regard to their mere externals or in regard to their contents. For American books, the American Catalogue is the most comprehensive bibliography, while other important ones are Scribner's Bibliographical Guide to American Literature (1856) and Duyckink's Cyclopaedia of American Literature. There are among bibliographies dealing with special subjects such works as The Literature of American History and Baker's Guide to the Best Fiction.