This is not a joke. Ethan Persoff, archivist of weirdo ephemera and "comics with problems," tells Boing Boing:

In 2011 Rick Santorum insulted the planet by comparing traditional marriage to a napkin. But did you know he ALSO wrote a short piece of fiction about "the birth of the napkin" in 2003? And to add further humor: This same book contains an endorsement of the Santorums from Bono of U2, and includes a foreword on "decent manners with children" by Joe Paterno.

Look inside "Karen Santorum's Dirty Book on Manners" at Ethan's website, and you can buy a copy on Amazon. One wonders if future printings will scrub the reference to Paterno (and if the Bono endorsement will stay?)