If someone enters a library today, it is well known that there is a system made out of sections, over topics, subjects and so on. They are there to help the visitor to orientate himself, to find his way through all those information. Librarians catalogue medias as books, DVDs, CDs or other visual and audiovisual medias to make our lives simpler. However, those systems variety from institution to institution and that is the problem.
Even if the reader knows where his favourite book is stored in his “home library”, it does not mean that he will find it in another library under the same section.
That could have multiple reasons, either the library has a more or less detailed system or the person who classified the book ,thought it belongs to another section. A book could be for one person belong to fiction, for another to art and for a third party to science. Finally, cataloguing is all about interpreting and personal thinking.
Eventually there are no uniform rules to classify books. The best we could do is to study all possibilities and bear the diversity of interpretation in mind.