Few writers are fortunate enough to write one great Batman story in their lifetime. Frank Miller has written two, with "Year One" being the second great Batman story. In fact, he's written both the best and second best Batman stories in DC. That's saying something considering there are plenty of amazing Batman stories written by other legendary writers. Within the span of one year, Frank Miller revolutionized "The Dark Knight." His influence can be felt throughout the comics and past and current Batman films (Including the Nolan Trilogy and the 90 Batman Films).
Following the death of Jason Todd (The second Robin after Dick Grayson), the Batman has retired. Skip ahead ten years and millionaire Bruce Wayne appears comfortable in his role as philanthropist. He cannot forgive himself for the death of Todd, but he finds it difficult to ignore the nagging voice in his head that he is needed back on the streets (I mean can you blame the man?).
To make things even more difficult, Gordon is just days from retirement and his replacement has a very firm stance against vigilantism (and men with incredible mustaches). The world has followed suit in this regard. It isn't just Batman who has hung up the cape. Wonder Woman has returned to Paradise Island, Green Lantern has disappeared in the stars, Green Arrow retires after losing an arm, and Superman has become a covert tool for the government (run by Ronald Reagan, surprisingly enough). The world has lost its heroes and, without Batman, the streets of Gotham have gone to hell. Crime is rampant and a new gang, calling themselves the Mutants, have the city in fear. Without a symbol to respect (and to fear), Gotham has fallen to chaos.
When Harvey Dent, having apparently been physically and psychologically made whole, begins committing crimes again Bruce is compelled to don the mantle of the bat once more. Batman's return jars his oldest nemesis, Joker, from ten year's of catatonia. Once and for all, Miller declares that Joker could not exist without the Batman and vice-versa.
What follows is a true masterpiece of storytelling. Scene after unforgettable scene propels Batman into near-fatal conflicts with the police and one final showdown with the Joker. It ends with a spectacular battle against Superman (This scene would later be used as inspiration for the BvS film), perhaps the most memorable moment in DC's history. It is in this book that the Batman of the next 20 years is forged. Indeed, Batman does return.
Overall, "The Dark Night Returns" is at it's core an amazing Batman story and helped set the standards on great comic book stories. The story also helped defy the notion that comic books are simply for children, due to its mature tone (along with "Maus" and "Watchmen") and subject matter which both demonstrate that comics can be a serious form of entertainment. So if you are bored one night at your local Barnes and Nobles (or anywhere else you can find comics) and want to read a good Batman story, then I would recommend reading "The Dark Knight Returns".