Books: Siddartha: to think about myself and my changes/voyage through life.

  Half-time: to think what-the-hell-comes-next (only if you are 40+)(it won't resonate with a 20yo)

  Systemantics, Nexus: if you work in mega-big-corpos this will save your life

  Hold on to your kids, The anxious generation: if you got kids

  Strong Fathers Strong Daughters: (and mothers/sons) if you got kids (too Christian-y for my taste but an amazing 'manual' to manage the relationship with your kid(s))

  1984, Animal Farm, Gulag Archipelago: ...

  Light on Yoga: (also do practice yoga, it's good for most-if-not-all)

All the listed ones are books I read and read again every few years. They shaped me the first time I read them, keep me 'grounded'/taking stock/thinking the 'change' in me and my life. I see them as a 'check-diff' and how I have changed/evolved/devolved since the last time I read it/them.