My journey into this world started with Watts' "The Way of Zen", and later, with his posthumous book "Tao: The Watercourse Way"

And I am a big fan of Ron Hogan's "Getting Right with Tao" translation/modern interpretation of the Tao Te Ching.

Lao Tzu: Tao Te Ching (Translated Ursula K. Le Guin) The Way of Lao Tzu (Wing-tsit Chan)