I've read dozens of self help books, and "How to Win Friends and Influence People" is in a league of its own. It is to self-help what "The Intelligent Investor" is to investing.

The only other self-help book I would put even close to it is, "The Subtle Art of Not Giving a Fuck" by Mark Manson. Its title sounds like it doesn't take itself seriously, but it's packed full of gems like this one:

“Everything worthwhile in life is won through surmounting the associated negative experience. Any attempt to escape the negative, to avoid it or quash it or silence it, only backfires. The avoidance of suffering is a form of suffering. The avoidance of struggle is a struggle. The denial of failure is a failure. Hiding what is shameful is itself a form of shame.
Pain is an inextricable thread in the fabric of life, and to tear it out is not only impossible, but destructive: attempting to tear it out unravels everything else with it. To try to avoid pain is to give too many fucks about pain. In contrast, if you’re able to not give a fuck about the pain, you become unstoppable." ~~~~ Mark Manson”