4 ideas
There he abducts young men and performs crude transorbital lobotomies on them with an ice pick, modelled on 1950s psychosurgery, hoping to create a permanently obedient 'zombie' companion. Every subject dies, and he keeps choosing new victims while his professor father, his family and his probation officer see only a troubled but manageable son.
The killer's aim is not death but a living person with no will of their own. He wants someone who will stay, submit and love him without being able to judge him or leave. Destroying the victim's autonomy while keeping the body alive is his answer to the terror of being rejected and to his inability to tolerate another person's separate mind.
Quentin avoids detection because his family's middle-class respectability, his compliant manner with therapists and probation officers, and his race and class make observers read him as low-risk. His victims are marginal young men whose disappearance draws little scrutiny. Look at who is believed and who is missed, and it becomes clear that systems are designed to overlook exactly this kind of predator.
The novel is written as Quentin's own disjointed notes, full of misspellings, capitalized fixations, blank gaps and sketches. There is no outside narrator to judge or explain him.