This post will serve as Part II of Philosophy Primary Sources and a supplement to Primary Sources & Encyclopedias (check out the Links section for even more research sources). There are certain books that are essential to an education about the human condition of which I believe should be available for free and with easy access to everybody. This list is more comprehensive and nuanced than the previous list, as it includes books that hold cultural significance in various fields of study. Each book on this list is in PDF format. I have organized them by topic (many topics intersect) and the last name of the author.
Philosophy
The Life of the Mind by Hannah Arendt
The Human Condition by Hannah Arendt
Language, Truth, and Logic by A.J. Ayer
The Problem of Knowledge by A.J. Ayer
Selected Writings of Jean Baudrillard
The Second Sex by Simone de Beauvoir
The Ethics of Ambiguity by Simone de Beauvoir
Matter and Memory by Henri Bergson
An Introduction to Metaphysics by Henri Bergson
The Myth of Sisyphus and Other Essays by Albert Camus
Language and Mind by Noam Chomsky
The God Delusion by Richard Dawkins
Nietzsche and Philosophy by Gilles Deleuze
What is Philosophy? by Gilles Deleuze & Félix Guattari
Darwin’s Dangerous Idea by Daniel Dennett
Speech and Phenomena & Other Essays by Jacques Derrida
Dissemination by Jacques Derrida
In Praise of Folly by Desiderius Erasmus
The Vocation of Man by Johann Gottlieb Fichte
The Science of Knowledge by Johann Gottlieb Fichte
The Archaeology of Knowledge & The Discourse on Language by Michel Foucault
Selected Writings of Mahatma Gandhi
Being and Time by Martin Heidegger
The Question Concerning Technology & Other Essays by Martin Heidegger
What is Metaphysics? by Martin Heidegger
God is Not Great by Christopher Hitchens
Logical Investigations by Edmund Husserl
Reason and Existenz by Karl Jaspers
Fear and Trembling by Søren Kierkegaard
The Sickness Unto Death by Søren Kierkegaard
Philosophical Fragments by Søren Kierkegaard
Last Writings: Nothingness and the Religious Worldview by Nishida Kitarō
The Levinas Reader edited by Sáun Hand
The Postmodern Condition by Jean-François Lyotard
On the Genealogy of Morals by Friedrich Nietzsche
The Portable Nietzsche edited by Walter Kaufmann
The Self-Overcoming of Nihilism by Keiji Nishitani
Philosophical Explanations by Robert Nozick
Man Has No Nature by José Ortega y Gasset
The Age of Reason by Thomas Paine
The Virtue of Selfishness by Ayn Rand
Contingency, Irony, and Solidarity by Richard Rorty
Philosophy and the Mirror of Nature by Richard Rorty
The Confessions of Jean-Jacques Rousseau
Free Thought & Official Propaganda by Bertrand Russell
In Praise of Idleness by Bertrand Russell
Mysticism and Logic: And Other Essays by Bertrand Russell
Being and Nothingness by Jean-Paul Sartre
Existentialism is a Humanism by Jean-Paul Sartre
The World as Will and Representation – Vol. 1 by Arthur Schopenhauer
The World as Will and Representation – Vol. 2 by Arthur Schopenhauer
The Basis of Morality by Arthur Schopenhauer
My View of the World (Excerpt) by Erwin Schrödinger
Athens and Jerusalem by Lev Shestov
The Ego and His Own by Max Stirner
The Courage to Be by Paul Tillich
The Eternal Now by Paul Tillich
Weak Thought edited by Gianni Vattimo and Pier Aldo Rovatti
The Wisdom of Insecurity by Alan Watts
Philosophical Investigations by Ludwig Wittgenstein
Science
The New Organon by Francis Bacon
The Grounds for and Excellence of the Corpuscular or Mechanical Philosophy by Robert Boyle
On the Revolutions of the Heavenly Spheres (Dedication) by Nicolaus Copernicus
On the Origin of Species by Means of Natural Selection by Charles Darwin
The Blind Watchmaker by Richard Dawkins
The Selfish Gene by Richard Dawkins
The Principles of Quantum Mechanics by Paul Dirac
Relativity: The Special and General Theory by Albert Einstein
The Assayer by Galileo Galilei
Dialogues Concerning the Two Chief World Systems by Galileo Galilei
A Brief History of Time by Stephen Hawking
Physics and Philosophy: The Revolution in Modern Science by Werner Heisenberg
The Grand Design by Stephen Hawking & Leonard Mlodinow
Treatise on Light by Christiaan Huygens
The Structure of Scientific Revolutions by Thomas Kuhn
The Copernican Revolution by Thomas Kuhn
The Mathematical Principles of Natural Philosophy by Sir Isaac Newton
Science and Hypothesis by Henri Poincaré
What is Life? by Erwin Schrödinger
Mind and Matter by Erwin Schrödinger
The Physics of the Healing by Ibn Sīnā (Avicenna)
Psychology
Man’s Search for Meaning by Viktor Frankl
The Complete Works of Sigmund Freud
The Principles of Psychology: Volume I by William James
The Principles of Psychology: Volume II by William James
Man and his Symbols by Carl Jung
Memories, Dreams, Reflection by Carl Jung
Religions, Values, and Peak Experiences by Abraham Maslow
Cognitive Psychology by Ulric Neisser
Verbal Behavior by B.F. Skinner
Literature
The Divine Comedy by Dante Alighieri
Don Quixote by Miguel de Cervantes
The Brothers Karamazov by Fyodor Dostoevsky
Crime and Punishment by Fyodor Dostoevsky
Notes from the Underground by Fyodor Dostoevsky
Euripides: Ion, Hippolytus, Medea, & Alcestis
Faust by Johann Wolfgang von Goethe
Brave New World by Aldous Huxley
The Complete Stories of Franz Kafka
In Search of Lost Time by Marcel Proust
Letters to a Young Poet by Rainer Maria Rilke
The Notes of Malte Laurids Brigge by Rainer Maria Rilke
The Complete Works of William Shakespeare
Note: Planet Publish hosts a vast selection of literature in PDF format available for free.
Religious
Deliverance from Error by Al-Ghazali
The Incoherence of the Philosophers by Al-Ghazali
The Summa Theologica by Thomas Aquinas
Institutes of the Christian Religion by John Calvin
The Vedas compiled by the Dharmic Scriptures Team
On Divine Names & Mystical Theology by Pseudo-Dionysius the Areopagite
The Shōbōgenzō: Volume I by Eihei Dōgen
The Shōbōgenzō: Volume II by Eihei Dōgen
The Shōbōgenzō: Volume III by Eihei Dōgen
The Shōbōgenzō: Volume IV by Eihei Dōgen
Dōgen’s Extensive Record: A Translation of the Eihei Kōroku
The Tibetan Book of the Dead edited by W. Y. Evans-Wentz
The Essence of Christianity by Ludwig Feuerbach
Christian Apologetics by Norman Geisler
Philosophy of Religion by Norman Geisler
The Principia Discordia by Greg Hill and Kerry Wendell Thornley
The Perennial Philosophy by Aldous Huxley
The Guide for the Perplexed by Moses Maimonides
The Mūlamadhyamakakārikā of Nāgārjuna
On Buddhism by Keiji Nishitani
The Upanishads translated by Swami Paramananda
On the Harmony of Religion and Philosophy by Ibn Rushd (Averroes)
The Incoherence of the Incoherence by Ibn Rushd (Averroes)
Forgotten Truth by Huston Smith
An Introduction to Zen Buddhism by D.T. Suzuki
The Bhagavad Gita translated by Shri Purohit Swami
Note: Internet Sacred Text Archive hosts an archive of online books about religion, mythology, folklore and the esoteric (including the writings of the early church fathers).
Historical
World History: Patterns of Interaction by Beck, et al.
The Diary of a Young Girl by Anne Frank
The Decline and Fall of the Roman Empire: Volume I by Edward Gibbon
The Decline and Fall of the Roman Empire: Volume II by Edward Gibbon
The Decline and Fall of the Roman Empire: Volume III by Edward Gibbon
The Decline and Fall of the Roman Empire: Volume IV by Edward Gibbon
The Decline and Fall of the Roman Empire: Volume V by Edward Gibbon
The Decline and Fall of the Roman Empire: Volume VI by Edward Gibbon
I Have a Dream by Martin Luther King Jr.
The History of Rome by Titus Livius
The History of Western Philosophy by Bertrand Russell
Anti-Semite and Jew: An Exploration of the Etiology of Hate by Jean-Paul Sartre
The Decline of the West by Oswald Spengler
The History of the Peloponnesian War by Thucydides
Note: Project Gutenberg and the Internet Archive are excellent sources of historical writings and much more. Ancient Greek and Roman histories can be found at Loebolus.
Important Historical Documents
Magna Carta Libertatum (Great Charter of Liberties)
Universal Declaration of Human Rights
Note: OurDocuments.gov hosts a list of 100 milestone documents, compiled by the National Archives and Records Administration, and drawn primarily from its nationwide holdings. The documents chronicle United States history from 1776 to 1965.
Political & Social Theory
On the Reproduction of Capitalism by Louis Althusser
An Introduction to The Principles of Morals and Legislation by Jeremy Bentham
Understanding Power: The Indispensable Chomsky
Anti-Oedipus: Capitalism & Schizophrenia by Gilles Deleuze & Félix Guattari
Discipline and Punish: The Birth of the Prison by Michel Foucault
The History of Sexuality by Michel Foucault
Madness and Civilization by Michel Foucault
The Theory of Communicative Action by Jürgen Habermas
Between Facts and Norms by Jürgen Habermas
Dialectic of Enlightenment by Max Horkheimer and Theodor Adorno
The General Theory of Employment, Interest, and Money by John Maynard Keynes
Structural Anthropology by Claude Lévi-Strauss
The Savage Mind by Claude Lévi-Strauss
The Prince by Niccolò Machiavelli
Capital: Critique of Political Economy, Volume I by Karl Marx
Capital: Critique of Political Economy, Volume II by Karl Marx
Capital: Critique of Political Economy, Volume III by Karl Marx
Economic and Philosophic Manuscripts of 1844 by Karl Marx
The German Ideology by Karl Marx & Friedrich Engels
The Spirit of Laws by Montesquieu
A Theory of Justice by John Rawls
Émile, or Concerning Education by Jean-Jacques Rousseau
The Origin of Inequality by Jean-Jacques Rousseau
The Social Contract by Jean-Jacques Rousseau
The Wealth of Nations by Adam Smith
Civil Disobedience by Henry David Thoreau
The Theory of the Leisure Class by Thorstein Veblen
The Protestant Ethic and the Spirit of Capitalism by Max Weber
Check out the Links Section for more sources of primary texts and general research.