Theoretically, it's paying homage to Clint Eastwood westerns (e.g. Yassa's neighbours, especially the hysterical preacher). In practice, though... John Ridgway. In scratchy, atmospheric black-and-white. With a John Wagner script that's set in the Cursed Earth and going deliberately slow and sinister, with a dead man for a title character and enemies who are a hundred times more undead than him. (The Dead Man isn't actually dead. Yassa just calls him that, because by all rights he should be. He fell into an acid river and he looks like Boris Karloff playing The Mummy.)
It's basically horror. Which you might have guessed when I said "John Ridgway".
What's interesting is that it's always great, no matter how often you reread it, even though at the time it was all about the mystery of "Who is the Dead Man?" That's huge, yes, but on rereading it's about its slow-building horror and its characters. The relationship between Yassa and the Dead Man. When and how hard he tries to ditch Yassa and send him away to safety. The rescues. The panel where the Grunts are about to carve up Yassa for food and one of them is holding a bowl to catch the blood.
I think it gets better on rereading, actually. The more time I spend with Yassa, Dog and the Dead Man, the more I want to follow them for longer.
If you read this, you'll also want to read Tale of the Dead Man (how he got that way), Countdown to Necropolis and Necropolis (the fall of Mega-City One and the death of 60 million people) and above all the next dozen or so Judge Dredd episodes. Because Yassa's in them.