"Taekwondo: The Korean Martial Art" Richard Chun. Harper and Row, 1976.
A very good overview of the martial art of taekwondo.

"Taekwondo: Secrets of Korean Karate" Sihak Henry Cho, Charles E. Tuttle Co., 1992.

"Zen Mind, Beginner's Mind" S. Suzuki, Weatherhill, 1972.
Informal talks on Zen meditation and practice by one of the most influential Zen teachers of his time.

"Zen in the Art of Archery" Eugen Herrigel, Vintage Books, 1989.
A German philosopher goes to Japan to learn about Zen through the study of archery. As noted by Suzuki in the forward, martial arts are not intended to be useful or for pleasure, but are meant to train the mind, to bring it into contact with the ultimate reality. The mind has to become attuned to the "Unconscious". One has to transcend technique so that the art becomes an "artless art" growing out of the Unconscious.

"The Book of Five Rings" Miyamoto Musashi, Random House, 1993.