I know that Priest themselves don't think very highly of it, but I've always liked this one. It derives an unsettling effect from its subtlety, and I can't detach it from the time it was made: Back in 1981, people actually were afraid of nuclear war and were afraid to see something like this in the sky some day. To me, it looks like a view taken from a window on a plane, and as a frequent flyer, I do occasionally think back to this cover and what it would be like if I'm sitting in a plane while nuclear holocaust is starting. Very effective.