His earlier books can drive a person crazy on one hand and his thoughts will never leave you on the other. Fear and Trembling is written from as a non-believer, Johannes DE SILENTIO, trying to understand God asking Abraham to sacrifice his son Isaac. The conclusion after 160 pages? He still had no idea. That journey of thought through the book 20 years later still travels with me. I'm okay not understanding or having an opinion on everything. That unusual for Theologian students (Not professors). Faith doesn't always = understanding or a complete knowledge. Now is important and those around you are. (Also helps to think that way after my 15 year old sister passed away from brain cancer and my son at 12 from bone cancer)
Also the BIG one for me was the idea of the Demonic Despair where a person's identity was in the tragic absurdness of themselves when not whole. Once we understand that we alone are responsible for having an identity in our experiences and to something higher then us lead me to a conversation with my mom. My mom is now an Licensed Counselor and her final thesis was based on Soren's "Acts of Love."
As a cancer dad who has lost a child I am in fairly large network of families that have also lost their child. There has been many times when the grief for friends have gotten so great that they ran into a life crisis. (Usually happens years after the death of their child)They think they are crazy and that they should have gotten to a place of acceptance (That doesn't really happen, at least in my case). There comes a place when you can't just accept your lot without just losing one's self. This leap onto faith seems to have happened with a few families and it really changed people's lives.