In his book A Guide to Collecting Librariana, Norman D. Stevens gives the following definition of librariana: "Those artifacts, including but by no means limited to printed materials, that depict any aspect of librarians, librarianship, and/or libraries; such artifacts, which are most typically of an ephemeral nature, may be those produced or used by librarians or libraries as well as those produced and used by others; they include, in particular, representations of librarians, librarianship, and/or libraries in the popular culture of society."
The term librariana (and library collectibles) is used on this blog to refer to artifacts, memorabilia, souvenirs, and collectibles related to libraries, librarians, and their history. Some blog posts are related to the representation of librarians and libraries in "the popular culture of society".
The collector of library artifacts and memorabilia can choose to be a generalist and collect a wide variety of artifacts and memorabilia related to libraries and librarians or he or she may choose to specialize in certain areas such as library postcards or library souvenir china or any number of the collecting categories listed below. The collector may also choose to collect items relating to a particular library such as the Library of Congress, a particular person such as Melvil Dewey, or a particular library organization such as the American Library Association. The Norman D. Stevens Collection of Library Architecture located at the Canadian Centre for Architecture is arguably the world's largest collection of librariana. Hans Krol has probably assembled a collection of similar scope. He has an amazing blog featuring librariana. I have a blog post about Stevens and Krol. Dan Lester was also a major collector of a wide variety of librariana. I helped him disperse his collection after retirement and his relocation to Utah. I collect a little of everything but I specialize in collecting postal librariana and library postcards.
While Stevens' book is the "bible" of librariana collecting, an important ongoing source of librariana is the series of Whole Library Handbooks by George Eberhart. Each of the handbooks has a chapter on librariana. The newest edition is The Whole Library Handbook 4.