The main character is Reginald Perrin, of course. He is the one around whom the whole story revolves. His actions, thoughts and feelings are what drive the narrative forward.
There is also his wife, Elizabeth Perrin. She plays an important role as she is part of the life that Reginald is trying to escape from. Her reactions and relationship with Reginald add depth to the story.
Well, the theme could also be seen as a critique of modern society. The novel shows how the expectations and norms of society can drive a person to extreme measures. Reginald's actions like faking his own death are a response to the stifling environment of work, family and social obligations. He tries to break free from the chains of what is considered 'normal' life in the modern world.
I'm not sure specifically as I haven't read the 'death notice novel' in detail. But usually in such novels, there is a protagonist who is likely to be someone involved in solving the mystery or facing the challenges related to the 'death notice'.
The main characters could include the god of death, of course. There might be a human character who has a special connection to the god of death, perhaps a seer or someone with a rare gift. And there could be a council of deities that the god of death has to interact with, whether they are allies or foes. These various characters would each contribute to the overall plot and theme of the novel.
Since I'm not familiar with the book, it's hard to say who the main characters are. But they could be humans who are involved in the robotics industry, like engineers or scientists. Or perhaps there are some special robots that are the focus, such as a robot detective or a powerful combat robot.
Since I don't know the specific 'death watch novel', I can't say for sure. But they could be the people on the death watch, like a doctor, a family member, or a professional caregiver.
Since I don't know the specific 'death crone novel', I can't say for sure. But likely, the death crone herself would be a main character. There might also be characters whose lives she affects, like a young hero who tries to stop her evil deeds if she's a villain, or a person seeking her wisdom if she has a more ambiguous role.
The main character is Gustav von Aschenbach, an aging writer. And then there's Tadzio, the beautiful young boy who becomes the object of Aschenbach's obsession.
I'm not entirely sure about all the main characters in the 'death stranding novel' since I haven't read it fully. But based on the game, in addition to Sam, characters like Mama, who has a special connection to a BT, could be important in the novel. There may also be new characters introduced in the novel that play crucial roles in the story, perhaps some leaders of the different settlements or people who have special abilities related to the chiral network.
I don't know specifically as I haven't read it, but there's likely to be the adept themselves (even though they die), and perhaps people close to the adept like friends, family, or colleagues.
The main characters in 'the death of superman novel' include Superman himself. Then there's Lois Lane, who has a deep connection with Superman. Also, other characters like Jimmy Olsen from the Daily Planet might be important. And, of course, the villains such as Doomsday who is probably the one responsible for Superman's death.