The Rational Male, Rollo Tomassi. Insight on how half of the world's population treats most men, and how not to become a slave .
I was going to ironically suggest this, not because it isn't good, but it's not exactly uncontroversial.
It is perhaps the single most important book for a young man to read as he enters the age of the sexual market. Even as a Christian striving to abstain from the casual sex ecosystem, I grasp so much more about gender dynamics because of Rollo's work. It turned me from the path of despair.
Bachelor Pad Economics is perhaps the single best practical guide to life for anyone living right now. He is extremely redpilled on just about every dimension of our society and offers cogent advice for navigating such a putrefied system as the one we live in. He's also relentlessly libertarian in an entertaining way.