University of Wisconsin-Milwaukee Special Collections Librarian Max Yela writes:
[The Colonel's Portentous Cat Unsays] is perhaps the most recent and remarkable of invisible books. It follows a long tradition of dream books and stories, from biblical citations of dream-state narratives, to the Hypnerotomachia Poliphili and Shakespeare’s Mid-Summer Night’s Dream, to Gabriel Garcia Marquez’s Eyes of a Blue Dog and Lane Hall’s Dream Snake. Until very recently the book’s existence was known only from an email correspondence between two friends:

Charlie Huenemann to Rick Krause on Aug 25, 2006:
Last night I dreamt I was in a coffeeshop in Chicago with you, telling you about a fabulous book I read. I explained it as “what you’d get if Kafka showed up in the village of Garcia Marquez’s ONE HUNDRED YEARS OF SOLITUDE….” The title was “The (something) (something) cat (something).” I woke up, and was disappointed to find there is no such book. Still, it’s a great title.

Rick Krause to Charlie Huenemann on August 26, 2006:
In my dream, if I remember correctly, the title of the book you described to me was (and probably still is) “The Colonel’s Portentous Cat Unsays.” The title contains a hint as to why the book cannot be found upon awakening and why it can only be vaguely remembered, much less recreated. As the book is read by the dreamer who stumbles upon it, the text unsays itself. Word by word, sentence by sentence, the text disappears after it has been read. Pages, too, disappear as they are turned. Every dreamer who begins reading “The Colonel’s Portentous Cat Unsays” is compelled to finish it in one sitting, for it contains exactly what the dreamer had hoped or feared it would contain. But there is no looking back, no retracing the narrative path, no returning to the book once it has been read. Waking dreamers are left with inchoate memories, ill-defined longings, poignant regrets . . .

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The Colonel’s Portentous Cat Unsays is one of nine invisible books on display in Max Yela’s exhibit:
Invisible Books from the Library of Babel
January 10-February 30, 2008
Main Floor, West Wing
UW-Milwaukee Libraries
2311 E. Hartford Ave
Milwaukee, Wisconsin