Also highly recommended:
Mahāyāna Buddhism: the doctrinal foundations by Paul Williams
The Awakening of Faith: attributed to Aśvaghoṣha by Yoshito S. Hakeda
The Surangama Sutra: A New Translation by Hsüan Hua OR Surangama Sutra by Lu-Kuan-Yu
Cultivating Original Enlightenment: Wonhyo's Exposition of the Vajrasamādhi-sūtra by Robert E. Buswell
The Sutra of Perfect Enlightenment: Korean Buddhism's Guide to Meditation (with commentary by the Sŏn Monk Kihwa) by A. Charles Muller
Zongmi on Chan by Jeffrey L. Broughton
Tracing Back the Radiance: Chinul's Korean way of Zen by Robert E. Buswell
"While teachers of the middle way, mind only, transcendent wisdom, mantra, and other schools may have their own assertions, the fulfillment of those intentions is the same. There is not a single thing that is not contained within mind."
(Gampopa to Düsum Khyenpa, in "The First Karmapa", KTD Pub, p254)
“If you recognize the world of appearance and existence as the mind, realize the mind itself as empty, and have no grasping at the superiority of your realizations — this is the ultimate view."
(Chegom Dzongpa, in "The Book of Kadam", Wisdom Pub, p609)