Sloterdijk's contemplation of our "In" draws from so many diverse sources, from St. Augustine to Heidegger, from the mystics who wrote about the internal life of the Holy Trinity to those who practiced psychoanalysis - it's breathtaking.
Moreover, Sloterdijk writes in a manner that appeals to both the devoutly religious and to atheists alike.
It's unfortunate that I read it during a period of my life when I was so preoccupied that I couldn’t elaborate more on this great book here.