The Death of Ivan Ilych is an extremely good short novella about a man's emotional experience with terminal illness.
Ivan realizes that he is going to die and is forced to process this idea throughout the entirety his long and drawn out death. He confronts his mortality in various specific ways which are indicative of a general attitude that is relatable but also flawed. The details of his attitude act as commentary on death and the flawed ways in which humans view it. He struggles with the idea of mortality, he knows that it is inevitable but he can't grasp the true nature of it. Ivan's emotional struggle is deeply moving emotionally and philosophically. I recommend this book to anybody since it is short and accessible while still being very powerful. Just don't read it if you don't like feeling sad.
SPOILERS BELOW
The book comments on the nature of mortality quite effectively, proving that death occupies our minds and robs us of the ability to perceive the meaning of life. Death lives rent free in our heads and tricks us into thinking there is nothing but death. This thought dominates Ivan's mind and conceals the good parts of life from him. A life lived with a focus on death is just a death drawn out over an entire lifespan.
Ivan's regrets mount as he realizes how much of his life was wasted climbing the social hierarchy and tolerating an unfulfilling family life. He wasted his life doing unfulfilling things. He may have been alive but he was not in touch with life. This is the sacrifice one makes when they favor the approval of the sinful and impure world over spirituality and personal fulfillment. He concludes that his life was a waste.
Ivan's butler Gerasim does not fear death, he lives a life where death doesn't occupy his mind as much as willpower and personal achievement do. Ivan in his last moments comes to view Gerasim as an example of moral success, and adopts a stoic attitude just before his death. In his last moments he shows pity for his friends and family, who are still hopelessly stuck in the unfulfilling lifestyle choices that he made.