Experience and Philosophy: a personal record of transformation and a discussion of transcendental consciousness: containing his Philosophy of Consciousness Without An Object and his Pathways Through To Space
Introceptualism
Transformations in Consciousness: The Metaphysics and Epistemology, containing Franklin Merrell-Wolff's Introceptualism, and a forward by the editor, Ron Leonard
On Having No Head: Zen and the Rediscovery of the Obvious
Head Off Stress
The Trial Of The Man Who Said He Was God (Douglas told me that this is his favorite book and the least-read one; if you check for used copies, search by title; "D.E. Harding" is the author)
The Spectre in the Lake
The Science of the 1st Person
Toolkit for Discovering Who You Are
Religions of the World
Look For Yourself, or The Science and Art of Self-realisation
Face to No-Face, Rediscovering Our Original Nature