Collaboration between pTerry and Neil Gaiman.

"You see, there was a bit of a mixup when the Antichrist was born, due in part to the machinations of Crowley, who did not so much fall as saunter downwards, and in part to the mysterious ways as manifested in the form of a part-time rare book dealer, an angel named Aziraphale. Like top agents everywhere, they've long had more in common with each other than the sides they represent, or the conflict they are nominally engaged in. The only person who knows how it will all end is Agnes Nutter, a witch whose prophecies all come true, if one can only manage to decipher them. The minor characters along the way (Famine makes an appearance as diet crazes, no-calorie food and anorexia epidemics) are as much fun as the story as a whole, which adds up to one of those rare books which is enormous fun to read the first time, and the second time, and the third time..."

The Internet has Crowley/Aziraphale yaoi.