1. 
The Fourth Dimension; Rudy Rucker; Houghton Mifflin, 1985
Absolutley mind blowing; Dr. Diane Voss, my former professor, had me read this for a class I took on "time". It helped me form for much of my current understanding of realitys' structure.
2.
Flat Land; Edwin Abbot; Dover Publications, 1880
This book helped reinforce Plato's "Allegory of a Cave", helping me to understand my condition.
3. 
The Mission of Art; Alex Grey; Shambala Press, 2001
Great art and writing?!? Yep. Alex really helped me to understand my purpose, a blessing and a curse, as an artist in this world.
4.
Concerning the Spiritual in Art; Wassily Kandinsky, 1911
I love Wassily. He tried to speak in a language few have the eyes to see.