Below is far from a complete list of the books I have found useful, but these are some of the best. Enjoy!
A Path with Heart, by Jack Kornfield: an masterwork. A must have. Vast, accessible, rich and deep. Buy this and read it twice, at least. A great place for both beginners and advanced meditators to start and finish. Only major problem is that is it so nicely written and gentle you might not realize how hard hitting it is. Assume it is very hard hitting and technical despite its friendly tone and you will get more out of it.
After the Ecstasy, the Laundry, by Jack Kornfield: a wonderful, reality-based, down-to-earth discussion of spiritual awakening.
In this Very Life, by Sayadaw U Pandita: straight-up, list-based, Burmese Vipassana at its practical best.
Wisdom Wide and Deep, A Practical Handbook for Mastering Jhana and Vipassana, by Shaila Catherine: Wow! What a book! A fantastic blend of traditional and modern influences. Visuddhimagga meeds Pa-Auk meets the West. I am so glad that she wrote this, as it was much needed.
Indestructible Truth and Secret of the Vajra World both by Reginald A. Ray. Page after excellent page, three things become clear: 1) this man knows what he is talking about, 2) he knows how to talk about it well, and 3) his heart is overflowing with the wish for others to understand the truth for themselves right now. Very, very highly recommended.
Practical Insight Meditation, by Mahasi Sayadaw: my favorite dharma book. Buy one and memorize it. The late Mahasi Sayadaw was one of the greatest instigators of the revolution in Vipassana over the last 70 years. He was a profound scholar and practitioner. If I see far, it is because I stand on the shoulders of this giant. This book is very short, to the point and practical. It contains the technique, the maps, i.e. what to do and what happens. Part is available on-line (see my links page) and the whole book is available through Amazon.com and others. Part of it is also available in the next book:
Living Dharma, edited by Jack Kornfield: the teachings of 12 living and recent Buddhist masters. Straight-up traditional wisdom from Thailand and Burma.
The Middle Length Discourses of the Buddha, translated by Bikkhu Nanamoli and Bikkhu Bodhi: many of my favorite suttas are in this text. If you want to reconnect with the best of the Buddha's original teachings, which I highly recommend, this is a great book to have. Some of these suttas are available at Access to Insight.
The Path of Purification (Visuddhimagga), by Bhadantacariya Buddhaghosa, translated by Bhikkhu Ñanamoli. This is the greatest of the Buddhist technical encyclopedias of meditation. Huge, hard reading, amazing. It draws extensively from the suttas and commentaries and adds a ton of practical information as well. It is detailed to the point of absurdity, but when that is what you want, nothing else will do. I firmly believe that all teachers who wish to teach in the Theravada tradition should: a) be at least Second Path, and b) have read this book at least once. You will be astounded at how much ultra-cool stuff is in this book if you are willing to deal with what a gigantic hog it is. Side note: if you are interested in Buddhist Magick, nothing else compares to this book. Available on BPS (Buddhist Publication Society, Sri Lanka).
The Path of Freedom (Vimuttimagga), by The Arahant Upatissa, translated from the Chinese by the Rev. N.R.M. Ehara, Soma Thera and Kheminda Thera. This is the first great Theravada encyclopedia of meditation. Visuddhimagga (above) was probably based on it (though some scholars claim otherwise, but regardless, they are very similar in many ways). Lost in the original Pali, it is translated back from a surviving Chinese manuscript. Much more readable than the Visuddhamagga, still quite comprenensive but not as detailed. It is very highly recommended. I like this one a lot. If you want to see how far Western Theravada Buddhism has fallen from the glory of it roots, read this book and then read basically any book by a modern, Western, non-monastic teacher. The difference brings tears to my eyes. Also on BPS.
Path to Deliverance, by Nyanatiloka: a classic, pocket-sized primer, a compilation and organization of some great original texts and commentaries with additional explanation. Hard to find, but very worth it. Technical, traditional, fundamental dharma, like the above two books but much shorter. If the Visuddhimagga should be read by all Theravada teachers, this should be read by all Theravada students. Also on BPS.
The Path of Serenity and Insight, by Henepola Gunaratana: a very thorough, scholarly, traditional treatment of the path of concentration and insight practices in the old texts and in practice. Similar to Path to Deliverance in some ways.
Mindfulness in Plain English, also by Venerable Henepola Gunaratana: sort of the opposite extreme on the same material. Very accessible and easy to read, but still of high quality. A great place to start.
A Still Forest Pool, The Insight Meditation of Achaan Chah, compiled and edited by Jack Kornfield and Paul Breiter: Achaan Chah's wisdom is simple, clear, and very deep. Excellent.
The Progress of Insight, by Mahasi Sayadaw: another fine treatment of the maps of spiritual progress. Available online for free at Access to Insight (see my links).
Buddhist Meditation in Theory and Practice, by Paravahera Vajirana Mahathera. Wow, where to start... This one is on par with the Visuddhimagga but more straightforward. It is relentlessly technical, traditional and has high standards. An amazing book in an old-school style for those who like that sort of old-school stuff at its best.
Insight Meditation, Practical Steps to Ultimate Truth, by Achan Sobin S. Namto. A very practical, straight-forward and excellent book on insight meditation. Highly Recommended.
Highly recommended are any of the writings of Thich Nhat Hanh, a modern Vietnamese master and rare teacher, available on Parallax Press. His writings are too extensive to review all of them here, but in general contain much deep and peaceful wisdom.
Cutting Through Spiritual Materialism, by Chogyam Trungpa: a classic on how to keep the spiritual path from becoming a monster. Shows up on a lot of book lists for a reason. While there is a lot of controversy about the life of Chogyam Trungpa, and rightly so, his books are great.
Transcending Madness, by Chogyam Trungpa: deep teachings on the cycles of life and wisdom, using the Six Realms as a framework.
The Myth of Freedom, by Chogyam Trungpa: very worthwhile, with a good treatment of the Bhumis, a Tibetan map of the stages of spiritual awakening.
Journey without Goal, by Chogyam Trungpa: short, to the point, high-level wisdom. Includes a great section on the Five Buddha Families.
The Path is the Goal, by Chogyam Trungpa: straightforward, short, to the point.
Training the Mind and Cultivating Loving-Kindness, by Chogyam Trungpa: traditional slogan training in compassion and emptiness, with a good explanation of ultimate and relative bodhichitta.
Dharma Paths, by Ven. Khenpo Karthar Rinpoche: a fine work on the path with the Tibetan Five Path model of awakening included.
Introduction to Tantra, by Lama Yeshe: a deceptively simple but very profound work. Emphasizes the basics common to all wisdom traditions.
Zen Mind, Beginner's Mind, by Suzuki Roshi: a classic, and on many reading lists for good reason.
The comic books of Tsai Chih Chung, such as The Roots of Wisdom, The Tao Speaks: Lao-Tsu's Whispers of Wisdom, Zen Speaks: Shouts of Nothingness, Wisdom of the Zen Master: The Quest for Enlightenment, The Dao of Zhuangzi: The Harmony of Nature, and Zhuangzi Speaks: the Music of Nature, are such great fun and contain a lot of deep wisdom within them. Not necessarily that practical, but his illustrations are brilliant and the message excellent.
Loving Kindness, The Revolutionary Art of Happiness, by Sharon Salzberg: a very simple and clear treatment of Loving-kindness, Compassion, Sympathetic Joy, and Equanimity practices. Good medicine for the weary heart. Very accessible. One problem is lack of mentioning the samatha jhanas.
A Heart as Wide as the World, by Sharon Salzberg: very similar heart-based feel to her other book, Loving Kindness. Easy but in a good way.
Lust for Enlightenment, by John Stevens: a fun, sometimes risque, always insightful treatment of passion and the spiritual path. Very sane reading. Highly recommended.
Tracing Back the Radiance, edited by Robert Buswell: the Chan (Zen) teachings of Chi Nul, a great Korean Master. A beautiful treatment of the higher stages of wisdom and the essence of the spiritual life. Great for people in the lower stages of enlightenment, such as stream enterers.
The Essential Rumi, by translated by Coleman Barks: Rumi is one of the most beloved spiritual poets in the world. His deep wisdom, humor, and depth of humanity are unsurpassed.
The Light of Wisdom, root text by Padmasambhava, commentary by Jamgon Kongtrul the Great and others: very advanced and very profound. I come back to this one often.
Healing with Form, Energy and Light, by Tenzin Wangyal Rinpoche: Shamanic Tibetan Bon, the wisdom of emptiness and magic. A fine treatment of the powers and using samatha practice as a basis for insight.
Wonders of the Natural Mind, by Tenzin Wangyal Rinpoche: it is amazing how easily he flips from the mundane to the profound and back again with such natural ease and fluency.
The Tibetan Yogas of Dream and Sleep, by Tenzin Wangyal Rinpoche: I keep this one on my bathroom shelf and never fail to find it inspiring, particularly as lucid dreaming is how I got into all this stuff in the first place.
Light on Enlightenment, by Christopher Titmuss, who has been one of my most helpful teachers because he pulled no punches: A traditional and list-based book from a very free and outspoken teacher.
An Awakened Life, also by Christopher Titmuss: hard-hitting and fresh essays on a wide range of spiritual topics from a man who knows.
When Things Fall Apart, Heart Advice for Difficult Times, by Pema Chodron: her writings are very clear, very human, very heart-based, very real, and very understanding of life. Performs as advertised. Very suitable for beginners.
The Wisdom of No Escape, by Pema Chodron: a skillful blend of no-holds-barred dharma and great gentleness. Very good for beginners and advanced students alike.
Moon in a Dewdrop, Writings of Zen Master Dogen, edited by Kazuaki Tenanhashi: Dogen founded Soto Zen, and his works are poetic, mysterious, and yet practical in the classic Zen style. A powerful antidote to the shadow-sides of Western Zen in which Zen is about anything other than awakening, as awakening was all Dogen cared about.
Insight Meditation, by Joseph Goldstein: simple wisdom from a teacher who has the uncanny ability to sometimes teach above his level of understanding.
Liberation in the Palm of Your Hand, by Pabonka Rinpoche, edited by Trijang Rinpoche, translated by Michael Richards: the oral teachings of the Lam-rim, or Tibetan stages of the path. A huge, deep, and very Tibetan book. Not light reading, but useful if you want to understand where they are coming from. Not that practical, in all honesty, but still allows you to understand the standard Tibetan dogmas.