I've written before about how one of the best things about Batman is how adaptable he is as a character. Owing largely to the fact that he descends from pulp vigilantes but was refined for the world of superheroes, he can work in almost any kind of story, from gritty, street-level crime to world-traveling adventure, and even the occasional trip to space alongside the Justice League. But the one thing that you very rarely see from Batman is a story where he has to deal with the supernatural.
I think there's a good reason for that, and it has a lot to do with his origin. Ghosts and demons and other assorted haints are, after all, an indication of an afterlife, and the more you remind readers that, in comics at least, death is a transitional inconvenience rather than a permanent state of being, the more they start to wonder just why this guy is so mad about a couple of murders. But that said, it has been done on occasion, and it has never, ever been done as well as it was in Peter Milligan, Kieron Dwyer, Dennis Janke and Mike Mignola's Dark Knight, Dark City, which is out this week in a new paperback.