The Museum of Modern Art is currently featuring an exhibit called
Book/Shelf which presents works that seek to expand the notion of what constitutes a book. Pieces include traditional book forms, video, prints, installations, assemblages, and other formats. Below are some works that intrigued me:

This piece by Lenore Tawney, an amazing mixed media artist, is composed of ink on cork and seeds on book pages.

Richard Long created this artist's book by staining the pages with water and mud from the River Avon.

Brian Belott created a piece made up of 66 illustrated books with collaged additions. The books were exhibited on a table and included this book, with pages overflowing and thick with altered additions.

Dieter Roth created this book with pages selected from over 6,000 collages, photographs, and drawings he made while at the Philadelphia Museum College of Art. I would have loved to flip through all the pages but it is presented under plexiglas.

John Latham took all 32 volumes of the Encyclopedia Britannica and transferred them first to 16mm black and white film in 1971 and later to video. He created this 6 minute 33 second silent film projecting one page per frame in a continuous loop. This still shot does not begin to capture the mesmerizing result.