Went to Costco earlier (specifically, the one in West Covina, CA.) and came across a few books of the Professor on sale. They're by New World Library, on sale for $11.99 (originally $20). They include:

Pathways to Bliss: Mythology and Personal Transformation
Thou Art That: Transforming Religious Metaphor
The Inner Reaches of Outer Space: Metaphor as Myth and as Religion
Flight of the Wild Gander
Myths of Light

Didn't see any of the major books but here's some for any followers of the Professor.