Artists' books take every possible form, participate in every possible convention of book making, every possible "ism" of mainstream art and literature, every possible mode of production, every shape, every degree of ephemerality or archival durability.
There are no specific criteria for defining what an artist's book is, but there are many criteria for defining what it is not, or what it partakes of, or what it distinguishes itself from...
Artists' books are a unique genre, ultimately a genre which is as much about itself, its own forms and traditions, as any other art form or activity. But it is a genre as little bound by constraints of medium or form...It's an area which needs description, investigation, and critical attention before its specificity will emerge.
From The Artist's Book as Idea and Form by Johanna Drucker
Podcast Interview Featuring Johanna Drucker Care of the "Bad at Sports: Contemporary Art Talk" Web site, Duncan MacKenzie interviews Johanna Drucker, chatting about her exhibition at the Center for Book and Paper Arts (at Columbia College Chicago, through December 2012) as well as her experience as a scholar and creator of artists' books.
A Brief History of Artists' Books Yale University Art Library provides a concise history of the artist's book, focusing on its historical precedents and mentioning its various incarnations over time including the illustrated books of William Blake, livres d'artistes and contemporary artists' books.