Definition According to William Katz (1969) a Reference book generally has the following qualities:
It is a miscellany of information organised for quick, convenient use.
Arrangement usually, but not always, follows some consistent plan such as alphabetical order for encyclopaedias, tabulor from for statistics, and chronological order in a history outline.
It usually gives only a bird's eyeview of the topic, rarely considers it in any depth.
It concentrates on facts. It is constructed for the reader who has definite questions, and does not raise questions of its own. For example, a treatise on philosophy or science may to written with the object of raising questions without possible answers. A reference work in be mine fields serves to answer questions the reader brings to these works.
The pragmatic test should not be whether the book can be taken from the library, but rather how consistently useful it is in answering reference questions. If it serves this purpose for either patron or librarian with any degree of regularity, it should be part of the reference collection - even if this means duplicating, the title in the main collection. For example, a book of etiquette maybe frequently used Jo answer specific queries, and may also be a popular general reading material. In this case there should be two or more copies - one for the reference collection and one or more to be checked out on a regular loan basis. (William Katz. Introduction to Reference Work: Vol. 1: Basic Information Sources. 1969 New York. McGraw-Hill Book Company. p12).
Reference books are of several varieties as indicated from the definition. Some are directory type, which give short answers to the immediate information requirement. They can be bibliographies, directories of institutions, year books, almanacs, time-table of events, dictionaries, glossaries, etc. They can be narrative texts such as Encyclopaedias, Annual Reviews Synoptic Writing, etc. William Katz (cited earlier) groups them in the following manner.