From the opening color text:
"So you want to really know what's going on? What if I were to tell you that our world is under attack from a demon lord and his allies, a race of extraterrestrial sorcerers? That this unholy alliance seeks to either make us their slaves or destroy us utterly?
"And that the demon lord himself leads the invasion under the benevolent guise of the childrens' TV host Barney the Dinosaur?"
The Jihad to Destroy Barney RPG And Writer's Guide is a fan-made supplement for GURPS 4th Edition describing a world in which a high demon is able to operate nearly openly in his quest to take over the world. Players play Jihaddi, those who have been made aware of the threat. The intended playstyle is a black comedy conspiracy, and the gamebook continually crosses the line between being serious roleplaying setting and parody of other dark conspiracy roleplaying settings.