Project Gutenberg

Founded in 1971, Project Gutenberg, or PG, (Wikipedia page) is the world's oldest electronic library. Its holdings number more than 50,000 works, almost exclusively in the public domain (under US copyright law), and are available at no cost over the Internet.

Dozens of public domain science books may be downloaded freely (libre and gratis) by subject.

• Mathematics: Bookshelf and Catalog
• Astronomy: Bookshelf and Catalog
• Physics: Bookshelf and Catalog

1. Albert Einstein:
   Relativity: The Special and the General Theory, 3^rd Ed.
2. Albert Einstein:
   The Meaning of Relativity: Four Lectures Delivered at Princeton, May, 1921
3. Joseph Louis Lagrange:
   Lectures on Elementary Mathematics
4. Karl Friedrich Gauss:
   General Investigations of Curved Surfaces of 1827 and 1825
5. George Boole:
   The Mathematical Analysis of Logic: Being an Essay Towards a Calculus of Deductive Reasoning
6. Felix Klein:
   On Riemann's Theory of Algebraic Functions and their Integrals: A Supplement to the Usual Treatises
7. Henri Poincaré:
   Science and Hypothesis
8. Augustus De Morgan:
   Elementary Illustrations of the Differential and Integral Calculus
9. Augustus De Morgan:
   On the study and difficulties of mathematics
10. Alfred North Whitehead:
    An Introduction to Mathematics
11. Bertrand Russell:
    Introduction to Mathematical Philosophy
12. John W. Moon:
    Topics on Tournaments
13. Hermann Weyl:
    Space--Time--Matter
14. Niels Bohr:
    On the Quantum Theory of Line-Spectra, Parts I and II
15. Niels Bohr:
    The Theory of Spectra and Atomic Constitution
16. Max Planck:
    Treatise on Thermodynamics
17. Josiah Willard Gibbs:
    On Multiple Algebra
18. Josiah Willard Gibbs:
    Elementary Principles in Statistical Mechanics
19. Paul Carus:
    The Foundations of Mathematics: A Contribution to the Philosophy of Geometry
20. Arthur Stanley Eddington:
    The Mathematical Theory of Relativity

Books Produced at Distributed Proofreaders

The books for which I did the overall assembly (termed “post-processing” at Distributed Proofreaders) are listed below.

1. Alexander McAulay:
   The Utility of Quaternions in Physics
2. Amos Emerson Dolbear:
   The Machinery of the Universe
3. Karl Weierstrass:
   Theorie der Abel'schen Functionen
4. Ernst Leonard Lindelöf:
   Le Calcul des Résidus et ses Applications à la Théorie des Fonctions
5. Arthur Stanley Eddington:
   Space, Time and Gravitation
6. Vito Volterra:
   Leçons sur l'Intégration des Équations Différentielles aux Dérivées Partielles
7. Michel A. Melkanoff et al.:
   A Fortran Program for Elastic Scattering Analyses with the Nuclear Optical Model
8. Leonard Eugene Dickson:
   First Course in the Theory of Equations
9. Jacques Hadamard:
   Four Lectures on Mathematics
10. Maurice Godefroy:
    La Fonction Gamma
11. Albert Ribaucour:
    Étude des Élassoïdes ou Surfaces A Courbure Moyenne Nulle
12. H. E. Slaught and N. J. Lennes:
    Solid Geometry with Problems and Applications (Revised edition)
13. Florian Cajori:
    A History of Mathematics
14. Arthur L. Baker:
    Elliptic Functions
15. Amos Emerson Dolbear:
    Matter, Ether, and Motion
16. Max Planck:
    Vorlesungen über Thermodynamik
17. Forest Ray Moulton:
    An Introduction to Astronomy
18. Philip H. Wicksteed:
    The Alphabet of Economic Science
19. John Maynard Keynes:
    A Treatise on Probability
20. Rudolf Clausius:
    Die Potentialfunction und das Potential
21. John Henry:
    Abrégé de la Théorie des Fonctions Elliptiques
22. Richard Chace Tolman:
    The Theory of the Relativity of Motion
23. Hugh Blackburn:
    Elements of Plane Trigonometry
24. Hermann Laurent:
    Sur les Principes Fondamentaux de la Théorie des Nombres et de la Géométrie
25. Thomas Roberts:
    Tappet and Dobby Looms: Their Mechanism and Management
26. Horace Bryon Heywood and Maurice Fréchet:
    L'Équation de Fredholm
27. Sylvanus Phillips Thompson:
    Calculus Made Easy
28. Wallie Abraham Hurwitz:
    Randwertaufgaben bei Systemen von Linearen Partiellen Differentialgleichungen erster Ordnung
29. Leo Koenigsberger:
    Vorlesungen über die Theorie der Hyperelliptischen Integrale
30. Ernest Vessiot:
    Leçons de Géométrie Supérieure
31. George Howard Darwin:
    Scientific Papers, Vol. V
32. Felix Klein:
    The Evanston Colloquium: Lectures on Mathematics Delivered From Aug. 28 to Sept. 9, 1893 Before Members of the Congress of Mathematics Held in Connection with the World's Fair in Chicago
33. Heinrich Emil Timerding:
    Die Analyse des Zufalls
34. David Bierens de Haan:
    Note sur une Méthode pour la Réduction d'Intégrales Définies et sur son Application à Quelques Formules Spécials
35. George Albert Wentworth:
    The First Steps in Algebra
36. Charles Briot and Jean Claude Bouquet:
    Théorie des Fonctions Elliptiques
37. Godfrey Harold Hardy:
    Orders of Infinity: The `Infinitärcalcül' of Paul Du Bois-Reymond
38. George Howard Darwin:
    The Tides and Kindred Phenomena in the Solar System
39. Godfrey Harold Hardy:
    A Course of Pure Mathematics
40. Kurt Hensel:
    Zahlentheorie
41. Max Planck:
    The Theory of Heat Radiation
42. Évariste Galois:
    Oeuvres mathématiques d'Évariste Galois
43. William Burnside:
    Theory of Groups of Finite Order
44. William Frank White:
    A Scrap-Book of Elementary Mathematics
45. John Venn:
    The Logic of Chance: An Essay on the Foundations and Province of the Theory of Probability, with Especial Reference to its Logical bearings and its Application to Moral and Social Science and to Statistics