The Best Batman story ever written and apparently the inspiration for large chunks of the upcoming Dark Knight. That is nothing but good news.
Telling the story of transition of power between the old school mafia, and the new "freaks" of Gotham, and the origin of Two Face, The Long Halloween is simply crazy good.
Don't like Superhero stories? I don't care. The art is noir dark and stunningly dynamic, the story is gripping, a page turner in the best way.
This might not be a case of genre expanding like say Watchmen
or The Dark Knight Returns. This is simply the genre at it's very, very, best and that's pretty damn good. This is The Godfather of super hero books.