Cosmic Consciousness. RM Bucke.
A hundred+ year old classic written by a person with personal experiences with the topic. It is still interesting reading, and has some current points: (1) Cosmic consciousness happens, either as glimpses or as lasting experiences. (2) There seems to be an evolutionary unfolding which could make cosmic consciousness ordinary among humans in the near or distant future.
Crooked Cucumber: The life and Zen teachings of Shunryu Suzuki. David Chadwick.
Transluscent Revolution. Arjuna Ardagh.
Sufism. James Fadiman.
The Way of the Pilgrim. Unknown author.
Beautifully describes the heart prayer.
I Need Your Love – Is That True? Byron Katie. (a couple of weeks ago)
Integral Spirituality. Ken Wilber. (public draft – read a couple of weeks ago)
As It Is. Tulku Urgyen Rinpoche. (some weeks ago)