When it comes to living, there’s no getting out alive. But books can help us survive, so to speak, by passing on what is most important about being human before we perish. In “The Existentialist’s Survival Guide: How to Live Authentically in an Inauthentic Age,” Gordon Marino has produced an honest and moving book of self-help for readers generally disposed to loathe the genre. It is a hybrid of memoir and meditation, a culminating work of philosophy developed after two decades of teaching and writing.

“The thinkers between...