I like to keep track of books that explore their form. Here is a short list of some interesting examples.
Book within a book: http://new.pentagram.com/2012/05/new-work-schiaparelli-and-prada/
Griffin and Sabine (book as correspondence of letters and postcards): http://chachic.wordpress.com/2012/02/17/postcard-love-griffin-and-sabine/
Artist’s Books (various): http://en.wikipedia.org/wiki/Artist%27s_books
Cream (art exhibit in book form) – http://www.hotbooks.co.uk/book_details.asp?b_id=472
If you know of some other books that may fit in this list add a link to the comments.