The word 'cathexis' is defined as "the concentration of mental energy on one particular person, idea, or object (especially to an unhealthy degree)."
The novel Cathexis is about one man's selfish refusal to accept reality. When Allistair P. Roddenham trips over the line of life and death, he learns, through his 'thread theory,' how his consciousness can live forever. While that's really neat and all, the novel spends a great deal of time exploring the lives of those impacted by Allistair's pursuit of existential discovery and the grief and loss instigated by his rigorous pushing of scientific inquiry.
Cathexis is a lot of things, but at its most essential it's an antagonism between the narrator and the characters in the how do deliberately doomed characters rebel against their creator? What is the difference between what is determined and what can be altered? What is power and where does it start and stop? It's a lot funnier than it sounds.