Out of all the recommended reading lists i encountered, one really stood out. A reading list by a not well known American writer called L. Ron Gardner. It is such a high quality list that it deserves to be mentioned entirely. His writings and his website electrical spirituality are highly recommended as well.
Spiritual Reading List
Advaita Vedanta
Highly Recommended
Ashtavakra Gita—Hari Prasad Shastri (tr.) (Other translations also available.)
Be As You Are: The Teachings of Ramana Maharshi—David Godman (Best introductory book on the teachings of Ramana Maharshi. )
Sat-Darshana Bhashya and Talks with Maharshi—Sri Ramanasramam (A learned devotee's in-depth consideration of Ramana Maharshi's teachings within the framework of Indian-yogic philosophy.)
Sri Ramana Gita—Ramana Maharshi (An utterly unique, ultra-profound text that details the function of the Amrita Nadi in the Self-realization process.)
Talks with Sri Ramana Maharshi—Ramana Maharshi (Must Reading. A truly great and inspiring book.)
(Note: Sat-Darshana Bhashya, Sri Ramana Gita, and TalksWith Ramana Maharshi are available at www.arunachala.org.)
Recommended
I Am That: Talks with Sri Nisargadatta Maharaj—Maurice Frydman
Vivekachudamani (Crest Jewel of Discrimination)—Swami Prabhavananda and Christopher Isherwood (Other translations of Shankara's teachings also available.)
Buddhism (Original)
Highly Recommended
Some Sayings of the Buddha—F.L.Woodward (Easily the finest presentation of the Buddha's teachings on meditation and contemplation.)
Recommended
A Popular Dictionary of Buddhism—Christmas Humphreys (Excellent dictionary.)
Buddhism: An Outline of its Teachings and Schools—Hans Wolfgang Schuman
Mindfulness in Plain English—Venerable Henepola Gunaratana (Best introductory book on Insight meditation.)
The Heart of Buddhist Meditation –Nyaponika Thera (Classic text on Insight meditation.)
The Living Thoughts of Gotama the Buddha—Ananda Coomeraswamy and I.B. Horner
The Way of Non-Attachment—Dhiravamsa (Unique, Krishnamurti-influenced book on Insight meditation.)
Buddhism (Tibetan)
Highly Recommended
A Treasure Trove of Scriptural Transmission: A Commentary on The Precious Treasury of the Basic Space of Phenomena—Longchen Rabjam (A marvelous, ultra-mystical text.)
Self-Liberation Though Seeing With Naked Awareness—John Myrdhin Reynolds (Compare this translation of/commentary on Padmasambhava's Yoga of Knowing the Mind and Seeing Reality to the inimitable W.Y. Evans-Wentz's in The Tibetan Book of the Great Liberation.)
Teachings of Tibetan Yoga—Gharma C.C. Chang (Wonderful Mahamudra presentation. Out of print but can be purchased used at Amazon.com.)
The Cycle of Day and Night—Namkhai Norbu (Outstanding Dzogchen meditation manual.)
The Golden Letters—John Myrdhin Reynolds (A scholarly exposition of the history and practice of Dzogchen with regard to the Garab Dorje, the first teacher of Dzogchen.)
The Precious Treasury of the Way of Abiding—Longchen Rabjam (A wonderful classic text.)
The Supreme Source—Namkhai Norbu (The fundamental tantric text of Dzogchen.)
The Tibetan Book of the Great Liberation—W.Y. Evans-Wentz (Mystical, mind-expanding translation of/commentary on Padmasambhava's Yoga of Knowing the Mind and Seeing Reality. Compare this translation and commentary to John Myrdhin Reynold's in Self-Liberation Through Seeing With Naked Awareness. Skip Carl Jung's ridiculous Psychological Commentary.)
Recommended
Naked Awareness—Karma Chagme
Tibetan Yoga and Secret Doctrines—W.Y Evans-Wentz
Wonders of the Natural Mind—Tenzin Wangyal (The essence of Dzogchen in the Native Bon Tradition of Tibet.)
Buddhism (Zen)
Highly Recommended
The Zen Teaching of Huang Po—John Blofeld
Recommended
Kensho, The Heart of Zen—Thomas Cleary
Selected Sayings from the Perfection of Wisdom—Edward Conze (Translations of important Prajnaparmita Sutras, including the Heart Sutra.)
The Diamond Sutra and the Sutra of Hui Neng—A.F. Price (tr.) (Other translations of these sutras available.)
The Practice of Zen—Gharma C.C. Chang
The Way of Zen—Alan Watts (Classic introductory text by the godfather of American Zen.)
The Three Pillars of Zen—Phillip Kapleau (Classic, popular Rinzai Zen text that emphasizes the satori experience.)
Tracing Back the Radiance: Chinul's Korean Way of Zen—Robert Buswell Jr.
Zen Mind, Beginners Mind—Shunryu Suzuki (Classic, ultra-popular Soto Zen text.)
(Notes: Scholarly types will enjoy Heinrich Dumoulin's Zen Buddhism: A History (India and China) and Zen Buddhism: A History (Japan), Vol. 2." Serious students of Buddhist philosophy will appreciate Gharma CC Chang's The Buddhist Teaching of Totality, which expounds the wonderful, all-embracing philosophy of Hwa Yen Buddhism relative to Zen. For those who love reading Zen, check out Thomas Cleary's numerous books at Amazon.com.)
Christianity & Judaism
Highly Recommended
Meditations on the Tarot—Valentin Tomberg (An astonishing journey into Christian Hermeticism.)
Meister Eckhart—("The Complete Mystical Work of Meister Eckhart" is the recommended book to get—but it costs $75. "Meister Eckhart," (tr. Raymond B. Blakney) is fine compilation of Eckhart's sermons, and goes for about $15. Scholarly types will want to supplement either of the aforementioned books with "The Mystical Thought of Meister Eckhart," by Bernard McGinn.
Recommended
Inner Christianity—Richard Smoley (A clear and thoughtful guide to the esoteric Christian Tradition.)
Jewish Meditation—Aryeh Kaplan
Open Mind, Open Heart—Thomas Keating (A classic, best-selling text on the contemplative dimension of the Gospel.)
The Mystic Christ—Ethan Walker (Excellent book for Christians.)
The Secret Book of John—Steven Davies (translator)
The Sermon on the Mount According to Vedanta—Swami Prabhavananda
The Work of the Kabbalist—S'ev Shimon Halevi
(Note: Scholarly types into Western Christian mysticism will love the fine texts by Prof. Bernard McGinn. Check out McGinn's The Presence of God: A History of Western Mysticism series. This four-volume series includes The Foundations of Mysticism, The Growth of Mysticism The Flowering of Mysticism, and The Crisis of Mysticism. Beyond this series, McGinn has also graced us with The Essential Writings of Christian Mysticism, an immensely rich anthology of the greatest Christian mystical literature. Selections in this volume include writings from such great mystics as Origen, Augustine, Dionysius the Areopagite, St. John of the Cross, Bernard of Clairvaux, Meister Eckhart, Nicholas of Cusa, John Ruusbroec, Thomas Merton, and many more. Relative to a scholarly consideration of Jewish Mysticism, I highly recommend Gershom Scholem's Major Trends in Jewish Mysticism. Not only is this text the canonical modern work on the nature and history of Jewish mysticism, it's also one of the most thoughtful and incisive academic considerations of mysticism in general.
Daism
Highly Recommended
Hridaya Rosary (Four Thorns of Heart-Instruction)—Adi Da Samraj (Excellent technical devotional-meditation book.)
The Knee of Listening—Adi Da Samraj (The best spiritual autobiography ever written.) Get a copy of the latest edition, but also get a copy of an earlier edition written under either Franklin Jones or Bubba Free John. These earlier editions, unlike later and current editions, contain Da's outstanding "Meditation of Understanding" instructions on the practice of "real meditation,"or "radical understanding."
The Liberator: The "Radical" Reality-Teachings of The Great Avataric Sage, Adi Da Samraj--Adi Da Samraj
The Method of the Siddhas—Adi Da Samraj (A truly great spiritual book. Out of print and only available used. Try to get a copy written under either Franklin Jones or Bubba Free John. The current revised edition of the book, entitled "My 'Bright' Word," lacks the direct visceral impact of the original text.
The Way of Perfect Knowledge: The "Radical" Practice of Transcendental Spirituality in the Way of Adidam—Adi Da Samraj
Recommended
He-And-She Is Me: The Indivisibility of Consciousness and Light In the Divine Body of the Ruchira Avatar—Adi Da Samraj
Ruchira Avatara Hridaya-Siddha Yoga: The Divine (and Not Merely Cosmic) Spiritual Baptism in the Way of Adidam—Adi Da Samraj
Santosha Adidam: The Essential Summary of the Divine Way of Adidam—Adi Da Samraj
The All-Completing And Final Divine Revelation to Mankind: A Summary Description Of The Supreme Yoga Of The Seventh Stage Of Life In The Divine Way Of Adidam—Adi Da Samraj
(Note: The four books on the Recommended List contain a number of the same essays. Nonetheless, there is enough unique material in each book to merit its reading. )
Hinduism (Yoga)
Highly Recommended
The Bhagavad Gita (Translations of: Eknath Easwaran; Swami Prabahvananda and Christopher Isherwood; S. Radakrishnan. Many other fine translations/annotations also available.)
The Yoga of Spiritual Devotion: A Modern Translation of the Narada Bhakti Sutras—Prem Prakesh (A simple, inspiring text on the spiritual path of love and devotion.)
Yoga Philosophy of Patanjali—Swami Hariharananda Aranya (The best account of classical yoga I've encountered. Many other fine translations/annotations also available.)
Recommended
Be Here Now—Baba Ram Dass (Classic introductory book on Eastern philosophy. An easy and enjoyable read.)
How to Know God—Prabhavananda and Isherwood (Best introduction to the yoga philosophy of Patanjali.)
The Essential Swami Ramdas—Swami Ramdas
The Gospel of Sri Ramakrishna—Swami Nikhilananda
The Synthesis of Yoga—Sri Aurobindo (If you appreciate this book and crave more Aurobindo, get a copy of The Life Divine.)
The Upanishads (Translations of: Mascara; Prabhavananda and Isherwood. Other fine translations also available.)
The Yoga Tradition—Georg Fuerstein (Outstanding reference book on the history, literature, philosophy, and practice of yoga.)
Kashmir Shaivism
Highly Recommended
The Doctrine of Recognition—Jaideva Singh (The basic introductory handbook to the abstruse philosophical system of recognition.)
The Doctrine of Vibration —Mark S.G. Dyczkowski (A scholarly analysis of the doctrines and practices of Kashmir Shaivism.)
The Philosophy of Sadhana—Deba Brata SenSharma (Outstanding text that deals clearly and exhaustively with the ultra-important topic of Shaktipat, the Descent of Divine Power, or Grace.)
The Triadic Heart of Siva—Paul Eduardo Muller-Ortega (An ultra-esoteric text about the Heart (Hridaya) as Ultimate Reality, Emissional Power, and Embodied Cosmos.)
Recommended
Kundalini, Energy of the Depths—Lilian Silburn
Siva Sutras: The Yoga of Supreme Identity—Jaideva Singh (The foundational text of Kashmir Shaivism.)
Spanda Karikas: The Divine Creative Pulsation—Jaideva Singh (An elaboration of the dynamic aspect of Transcendental Consciousness.)
Miscellaneous
Highly Recommended
First and Last Freedom—J. Krishnamurti (Must reading for all mystics. If you appreciate this book and want to read more Krishnamurti, get his multivolume Commentaries on Living.)
Introduction to Objectivist Epistemology—Ayn Rand (Must reading for all mystics.)
Objectivism: The Philosophy of Ayn Rand--Leonard Peikoff (Must reading for all mystics.)
The Way of Chuang Tzu—Thomas Merton (Other translations also available.)
Recommended
Alan Oken's Complete Astrology—Alan Oken (The best overall book on astrology.)
Ayurveda: The Science of Self-Healing—Vasant Lad (A fascinating and enlightening exposition of the principles and practical applications of Indian Ayurveda, the oldest healing system in the world. )
Awaken Healing Energy Through the Tao—Mantak Chia (Classic introductory handbook to the practice and principles of Taoist energy-yoga.)
Return to The One: Plotinus's Guide to God-Realization –Brian Hines (An accessible modern exposition of an Ancient Classic, the Enneads.)
The Power of Now—Echart Tolle (Uberpopular best-selling text on the spiritual practice of Presence. A good book for spiritual beginners.)
The Ayn Rand Lexicon—Harry Binswanger (Objectivism from A to Z.)
The Perennial Philosophy—Aldous Huxley
The Tao Teh Ching (Numerous translations available.)