Webster defines the word "book" as 1 a : a set of written sheets of skin or paper or tablets of wood or ivory b : a set of written, printed, or blank sheets bound together into a volume c : a long written or printed literary composition. Library science uses the term "monograph" to distinguish what we commonly refer to as "books" from other printed materials, such as journals and periodicals. In the past three years, the term "book" has expanded to include electronic texts, such as e-books.
All of these definitions and connotations imply that books are works whose texts are in one discernible physical or electronic space. For cataloging purposes, this is a convenient assumption. Imagine the chaos if every page of one book was in a different place in the library? Or worse, if every page were in a different library? What if the book were divided into single words and scattered throughout the world? What about non-textual parts of a book?
While authors have often tested the boundaries of the book medium, the last decade (or two) has brought a new wave of expansion. Author Brandon J. Mendelson wrote a novel using only Twitter posts. The BBC Audiobooks America begin the Twitter novel project, a collaborative novel written by the followers of BBCAA. In Japan, some of the top selling novels were written by text message. And my personal favorite, author Shelley Jackson has written a short story, "Skin." Each word of the story is to be tattooed on a different person around the globe, effectively transforming people into the medium for her book.
Some may argue against defining these works as books, describing "book" as a medium rather than an intellectual endeavor. Nevertheless, that controversy, that debate is what makes this so exciting. However we describe these works, the task of defining them is one of the newer challenges to the field of library science. To put something into a category (as loose as it may be) allows the public to find it, access it, read it. Let the cataloging begin!