Make Room! Make Room! — Harry Harrison

A detective hunts down a killer in a dystopian, overpopulated NYC in this classic science fiction novel that inspired the film Soylent Green.
 
Originally published in 1966, Make Room! Make Room! imagines a world at the end of the twentieth century where Earth is so overwhelmed by rampant population growth that it teeters on the edge of self-destruction. In New York City alone, thirty-five million people are squeezed into its packed boroughs, scrambling like rats for the world's dwindling resources. The only food available is a product called soylent. And while the government tries to maintain order, the rich get richer and the poor stay underfoot.
 
Finding a killer in this broken world is one hell of a job. But that's exactly what Det. Andy Rusch has been assigned to do. If he can stay alive long enough, he might just solve the biggest case he's ever been on -- unless humanity finally fulfills its promise and destroys itself first.