These are some books I would recommend for those who are new to Zen practice and for those who wish to go deeper. They are roughly in the order I would suggest reading them but feel free to ignore that completely!
Introductory Books
Everyday Zen by Charlotte Joko Beck (also Nothing Special by the same author)
Hardcore Zen by Brad Warner
What is Zen? – Norman Fischer and Susan Moon
Most Intimate by Enkyo O’Hara
Zen Mind, Beginners Mind by Shunryu Suzuki (also Not Always So by the same author)
What the Buddha Taught by Walpola Rahula
Returning to Silence by Katagiri Roshi
Opening the Hand of Thought by Uchiyama Roshi
To Meet the Real Dragon by Gudo Nishijima
One Robe, One Bowl by Ryōkan (poetry)
Books For Going Deeper
The Art of Just Sitting by John Daido Loori (ed)
How to Cook Your Life by Uchiyama Roshi
Being Upright by Reb Anderson (Zen ethics)
The Zen Master’s Dance by Jundo Cohen
The Life of the Buddha by Bhikkhu Nanamoli
The Circle of the Way by Barbara O’Brien (a history of Zen from the Buddha to modern times)
Cultivating the Empty Field by Taigen Dan Leighton (teachings of the Chinese Zen master Hongzhi)
The Zen Teachings of Homeless Kodo by Kosho Uchiyama & Shohaku Okumura
Moon in a Dewdrop by Kazuaki Tanahashi (translations of Zen master Eihei Dōgen)
Living by Vow by Shohaku Okumura
Important Books from the Sōtō Zen Lineage
Shōbōgenzō (The Treasury of the True Dharma Eye) by Eihei Dōgen (translations by Nishijima Roshi & Chodo Cross in four volumes and/or Kazuaki Tanahashi)
Denkōroku (Transmission of Light) by Keizan Jōkin translated by Thomas Cleary or Francis Cook
Fortunate Way Zen 福 道 