"Batman: The Dark Knight" as it was originally called is a turning point in the Batman myth and in the evolution of the American Superhero genre in general. The four issues that make up the complete story represent a break from kid-friendly tales of good vs evil to more 'real world' examinations of heroic mythology; its origins and its ramifications both personal and societal. Written by Frank Miller it sent shock waves through the comic book world that are still being felt today. Some critics decried the loss of innocence, others embraced it with a hearty "It's about time!" But no one could ignore it.
Presaging Alan Moore's savage deconstruction of the superhero in "Watchmen" which would debut later the same year, Batman: The Dark Knight tells the tale of a middle aged and long retired Batman being pulled back into service to help restore order to a Gotham that has gone to seed in his absence. He's at first ineffective. In fact if it were not for the intervention of a 13 year old girl he probably would have died at the hands of a gang leader. But he recovers and as his profile beings to rise once again he's hounded by the media and his motives constantly questioned. When his campaign to clean up Gotham begins to meet with real success the state begins to see him as an enemy and sets out to destroy him by pitting a seemingly invicible opponent against him. The ending implies complex and troubling times ahead and even slyly begs the question later asked directly by Moore; "Who watches the (insert Superhero name of choice here)?"
After the success of the four individual issues DC released them together in a boxed set and the whole series took the name of the first issue: "The Dark Knight Returns". But whether you call it Batman: The Dark Knight or The Dark Knight Returns the story represents Batman's transition from Modern to Postmodern superhero. It's occassionaly gripping, always visually arresting and may be the most influential comic book mini-series of all time.