Well, in 'the dark knight returns story', the story is set in a future Gotham. Batman has been retired for a while. But crime is rampant, and he decides to come back. He starts to fight against the crime lords and also has to handle the return of his arch - nemesis, the Joker. And there are also some political and social elements as the city and the authorities react to Batman's return.
One of the main themes is the idea of an aging hero. Batman is older but still feels the need to fight for justice in Gotham. Another theme is the corruption and decay of society. The city has gone downhill, and Batman emerges from retirement to try and combat it.
In addition to those, there are other characters like Carrie Kelley who becomes the new Robin in the novel. She adds a new dynamic to Batman's world. There's also Superman, who has a complex relationship with Batman in this story. Superman represents the establishment and the government's power, while Batman is more of a vigilante figure. Their interactions are crucial to the plot.
Yes, Batman did kill in The Dark Knight Returns comics in some instances, but it was within a specific context and for particular reasons related to the storyline.
In this novel, Batman is front and center. He's the aging hero trying to reclaim his city. Commissioner Gordon, his old ally, is a key figure. The Joker, as always, is a major character, bringing his brand of madness. And we can't forget about Harvey Dent, Two - Face, who adds to the complexity of Gotham's criminal underworld. There's also Carrie Kelley, a young girl who becomes Robin and provides a different perspective.
One of the main themes is the idea of an aging hero. Batman is older but still feels the need to fight crime in a Gotham that has changed. Another theme is the blurring of the line between hero and vigilante. His extreme methods raise questions about justice. Also, the corruption in Gotham and society's reaction to Batman's return are important themes.