Intermediate:
Buddhism Without Beliefs by Stephen Batchelor
Opening the Hand of Thought by Kosho Uchiyama
Thoughts Without a Thinker by Mark Epstein
Mind of Clover by Robert Aitken, Roshi
Instructions to the Cook by Roshi Bernie Glassman and Rick Fields
Just Sitting edited by John Daido Loori, Roshi
Appreciate Your Life by Hakuyu Taizan Maezumi, Roshi

Advanced:
Moon In A Dewdrop by Eihei Dogen Zenji and Kazuaki Tanahashi
Cultivating the Empty Field by Zen Master Hongzhi
Verses From the Center by Stepehen Batchelor
Essence of the Heart Sutra by the Dalai Lama
The Teachings of Bodhidharma by Red Pine
The Diamond Sutra and the Sutra of Hui-Neng by A.F. Price, et al