The only book available in the West which clearly explains the philosophy, principles, and practice of Zen, "The Complete Book of Zen" draws upon the fundamental teaching of Hui Neng's Platform Sutra, considered by many to be the "bible" of Zen Buddhism.
Interesting historical/philosophical overview on the development of Chinese/Japanese/non-Buddhism Cha'an thought and practice, including the importance of Kung Fu and Qi Gong cultivation. Apparently Wong Kiew Kit teaches workshops on these in Malaysia...