I have found these books inspiring and/or informative:

Alan Wallace: The Attention Revolution: Unlocking the Power of the Focused Mind, Wisdom (A modern description and commentary on the text Stages of Meditation)

Alan Watts: Alan Watts Teaches Meditation (tape), Audio Renaissance  (Excellent, gritty teaching by the Oxford philosopher)

Alan Watts: The Two Hands of God, Collier (Interesting survey of dualism over various cultures)

Alan Watts: The Way of Zen, Vintage

Alan Watts: The Wisdom of Insecurity, Vintage

Anthony Molino: The Couch and the Tree, Constable

B. K. S. Iengar: Light on Yoga, Schocken (Comprehensive source on yoga)

Barry Long: Only Fear Dies, Barry Long Books

Brunton: A Search in Secret India, Weiser

Carolyne Rose Gimian: The Essential Chogyam Trungpa, Shambhala

Ch'an Master Sheng-Yen: Complete Enlightenment, Shambhala

Chandrakirti/Mipham: Introduction to the Middle Way, Shambhala

Chogyam Trungpa: Glimpses of Abhidharma, Shambhala

Chuang Zu: Inner Chapters, Amber Lotus

Clive Erricker: Teach Yourself Buddhism, Hodder & Stoughteh

Dakpo Tashi Namgyal: Mahamudra - The Moonlight, Quintessence of Mind and Meditation, Wisdom

Dalai Lama: Ancient Wisdom, Modern World, Little, Brown & Co.

Dalai Lama: Dzogchen, Snow Lion

Dalai Lama: Healing Anger, Snow Lion

Dalai Lama: Mind Science, Wisdom

Dalai Lama: Opening the Eye of New Awareness, Wisdom

Dalai Lama: How to See Yourself As You Really Are, Atria

Dalai Lama: Stages of Meditation, Rider

Dalai Lama: The Gelug/Kagyu Tradition of Mahamudra, Snow Lion

Dalai Lama: The Heart of the Buddha's Path, Thorsons

Dalai Lama: The World of Tibetan Buddhism, Wisdom

Daniel P. Brown:  Pointing Out the Great Way - The Stages of Meditation in the Mahamudra Tradition, Wisdom

Dave Lowry: Moving Towards Stillness, Tuttle

David Godman: Be As You Are, Penguin

David Servan-Schreiber: the Instinct to Heal, Rodale

Dilgo Khyentse: Guru Yoga, Snow Lion

Dogen: Moon in a Dewdrop, North Point Press

Eckhart Tolle: The Power of Now, Hodder Mobius

Freemantle & Trungpa: The Tibetan Book of the Dead, Shambhala

Garfield: The Fundamental Wisdom of the Middle Way, Oxford

Gia Fu Feng and Jane English: Tao Te Ching, Vintage

Herrigen: Zen in the Art of Archery, Vintage

J. Krishnamurti and David Bohm: The Limits of Thought, Routledge

Jack Kornfield: After the Ecstasy, the Laundry , Bantam

James Green: The Recorded Sayings of Zen Master Joshu, Shambhala (One of the great Chinese Ch'an (Zen) masters)

Jean-Francois Revel & Matthieu Riicard: The Monk and The Philosopher, Thorsons

Jeffrey Hopkins : Cultivating Compassion, Broadway

Jeffrey Hopkins : Meditation on Emptiness, Wisdom (Scholarly exposition of the Prasangika view of emptiness according to the Tibetan Gelukpa traditon)

Kai Kermani: Autogenic Training, Souvenir

Karma Chagme: A Spacious Path to Freedom, Snow Lion

Keith Johnstone: Impro - Improvisation and the Theatre, Routledge

Khenchen Thrangu: The Practice of Tranquillity  and Insight, Snow Lion

Krishnamurti: Total Freedom, Harper Colns

Kubler-Ross: On Death and Dying, Macmillan

Lama Thubren Yeshe: Introduction to Tantra, Wisdom

Lama Thubren Yeshe: The Bliss of Inner Fire, Wisdom

Lex Hixon: Mother of the Buddhas, Quest

Lhundup Sopa, Jeffrey Hookins: Cutting through Appearances, Snow Lion

Longchen Rabjam: A Treasure Trove of Scriptural Transmission , Padma

Longchen Rabjam: The Basic Space of Phenomena, Padma

Longchen Rabjam: The Practice of Dzogchen, Snow Lion

Longchen Rabjam: The Precious Treasury of the Way of Abiding, Padma

Longchenpa: You Are the Eyes of the World, Snow Lion

Michael Roach: The Tibetan Book of Yoga, Doubleday

Namkhai Norbu: Dream Yoga and the practice  of Natural Light, Snow Lion

Namkhai Norbu: Dzogchen and Zen, Blue Dolphin

Namkhai Norbu: Dzogchen: The Self-Perfected State, Snow Lion

Namkhai Norbu: The Crystal and the Way of Light, Snow Lion

Namkhai Norbu: The Cycle of Day and Night, Station Hill

Namkhai Norbu: The Supreme Source, Snow Lion

Padmasambhava: Natural Liberation, Wisdom

Pema Chodron: When Things Fall Apart , Element

Peter D. Santina: The Tree of Enlightenment, Chico Dharma Study Foundation

Peter Fenner: Intrinsic Freedom, Millenium

Peter Fenner: Radiant Mind: Awakening Unconditioned Awareness, Sounds True

Peter Fenner: The Edge of Certainty, Nicolas Hayes

Pettit: Mipham's Beacon of Certainty, Wisdom

Polly Young-Eisendrath: Awakening and Insight, Brunner-Routledge

Poonja: The Truth Is, Weiser

Prendergast, Bradford: Listening from the Heart of Silence, Paragon House

Prendergast, Fenner, Krystal: The Sacred Mirror, Paragon House

Ray: Secret of the Vajra World, Shambhala

Reynolds: The Golden Letters, Snow Lion

Rubin: Psychotherapy and Buddhism, Plenum

S. Rinpoche: Buddhist Meditation, The Theosphical Publishing House, Advar

Santideva: The Bodhicaryavatara, Oxford

Sharda Tashi Gyaltsen: Heart Drops of Dharmakaya, Snow Lion (Dzogchen practice from the Tibetan Bon tradition)

Shunryu Suzuki: Zen Mind, Beginner's Mind, Shambhala (One of the great modern Zen classics)

Sogyal Rinpoche: Glimpse after Glimpse, Rider

Sogyal Rinpoche: Meditation: Bringing the Mind Home, Rigpa Fellowship

Sogyal Rinpoche: The Tibetan Book of Living and Dying , Harper Collins

Sri Nisargadatta Maharaj: I Am That, Acorn

Sri Nisargadatta Maharaj: The Ultimate Medicine: Dialogues with a Realized Master, North Atlantic Books

Sri Nisargatta Maharaj: Consciousness and the Absolute,

Stephen and Adndrea Levine: Who Dies?, Anchor

Sue Gerhart: Why Love Matters, Brunner-Routledge

Swami Sri Ramanananda Saraswathi: Lamp of Non-Dual Knowledge, Cream of Liberation, World Wisdom

T. K. V. Desikachar: The Heart of TYoga, Inner Traditions International (Introduction to Yoga Theory and Practice)

Tenzin Wangyal Rinpoche: The Tibetan Yogas of Dream and Sleep, Snow Lion

The Ninth Karmapa: The Mahamudra - Eliminating the Ignorance of Darkness , LTWA

Thurman: The Tibetan Book of the Dead, Wisdom

Tulku Thondup: Boundless Healing, Shambhala

Tulku Thondup: The Healing Power of Mind, Shambhala

Yoel Hoffman (translator & commentator): Radical Zen - The Sayings of Joshu, Hoffman (One of the great Chinese Ch'an (Zen) masters)

Zajonc: The New Physics and Cosmology, Oxford