If you are curious about the inner mind of a Paranoid Schizophrenic or his mother, "Lowboy" by John Wray provides what seems to be a good representation. If, on the other hand, you are hoping for a strange detective story with psychological undertones, look elsewhere. ( I recommend "The Alienist".)

“Lowboy” is a teenaged paranoid schizophrenic with a criminal past whose whereabouts are unknown for one day. The novel focuses on his “travels” through the dark streets and subway tunnels of New York during the day and his mom’s “quest” to find him with the help of an overly-concerned detective.

Part of Lowboy’s delusions give him the impression that through his actions (whether or not he has sex), he can somehow lessen the effects of global warming. I found this one of the most touching parts of the story, as the desire to feel important is something that helps us all get through our day to day lives. In the book, the only people who truly understand this are other mentally ill people he comes in contact with.  
 
Like many paranoid schizophrenics, Lowboy does not have very many relationships. His  relationship mother, who he sends encrypted messages to, is the most important relationship he maintains in his life. His other primary relationship is with a former classmate whom he is technically not allowed to see any more due to a transgression in the past, which is definitely outside the realm of most normal relationships. She seems  at once captivated by his strangeness and slightly put off by it, primarily due to an incident mentioned in the book that I will not spoil here.  It is also difficult to understand whether her renewed friendship with Lowboy stems from her own desire to see him, or more of an interest in upsetting her father, who has (for very good reasons) forbidden her to see him. The bond he makes with the other mentally ill people in the story run deep because they are not forced to view the world in a "normal way".

As the novel progresses, the mother, who is an immigrant, remains concerned for Lowboy, but is not convinced he is “dangerous”, which is the detective’s belief. This contradiction brings up some of the issues facing the mentally ill, including the stigma associated with mental illness, and the idea that once someone has committed a crime in the past, they are forever vulnerable to committing a similar crime again.