Make Room! Make Room!
(First, for the record, that is not the cover of the edition I read. But it's such a great design that I had to show it to y'all.)
This book inspired the classic flick Soylent Green, but doesn't actually have much in common with that movie. Let me just put this up front: it's not people. It's soy + lentil (soylent). And that's not even a plot point.
This is a dark little look at population growth predictions from the 60s. Mass starvation, water riots, people dragging themselves through life as a matter of habit. It's no The Sheep Look Up, but it's not exactly a stroll through Peppyville, either. (Then again, do I really want to go to Peppyville? You just know all their restaurants make their employees sing to you when you just want to eat.)
Luckily, Harrison bundles bleak forecasting with a little mystery, a little drug use, a little sex, and a little sharp humor. That's a lot to pack into a slim novel, and it keeps you reading. Even if the main point isn't "People! They're eating people!" but, instead, "Wear your condoms, kids, there's not enough to go around."