💡 About this free book collection. Below are some of the highest-quality university textbooks that you can legally read and download for free. Each entry lists the title (in bold), the author(s) in italics, and the available formats with notes on whether a sign-up is required. Links point directly to the free books – I have manually checked the link quality (by hand).
- Structure and Interpretation of Computer Programs – Harold Abelson & Gerald Jay Sussman (HTML, no sign-up) – the classic MIT programming text is released as an open-access web edition under a Creative Commons license
- The Feynman Lectures on Physics – Richard P. Feynman, Robert B. Leighton & Matthew Sands (HTML, no sign-up) – Caltech’s website hosts the complete three-volume lecture series free of charge.
- Deep Learning – Ian Goodfellow, Yoshua Bengio & Aaron Courville (HTML, no sign-up) – the authors and MIT Press offer a complete online version that will remain freely accessible.
- Operating Systems: Three Easy Pieces – Remzi H. Arpaci-Dusseau & Andrea C. Arpaci-Dusseau (PDF, no sign-up) – a comprehensive OS text that the authors explicitly intend to remain freely available.
- Category Theory for Scientists – David I. Spivak (PDF, no sign-up) – MIT’s open-courseware site links to this freely downloadable textbook.
- Algebraic Topology – Allen Hatcher (PDF, no sign-up) – the author and publisher allow free download of this standard graduate-level text.
- Linear Algebra – Jim Hefferon (PDF & HTML, no sign-up) – Hefferon’s textbook is free to download and is licensed for redistribution.
- Introduction to Real Analysis – William F. Trench (PDF, no sign-up) – a free, Creative Commons–licensed edition of this undergraduate text.
- Abstract Algebra: Theory and Applications – Thomas W. Judson (PDF, no sign-up) – an open textbook published under the GNU Free Documentation License.
- Introduction to Probability – Charles M. Grinstead & J. Laurie Snell (HTML & PDF, no sign-up) – the authors distribute this complete text under a free documentation license.
- The Elements of Statistical Learning – Trevor Hastie, Robert Tibshirani & Jerome Friedman (PDF, no sign-up) – a highly regarded machine-learning reference with a free PDF.
- Reinforcement Learning: An Introduction – Richard S. Sutton & Andrew G. Barto (HTML & PDF, no sign-up) – the authors provide free HTML and PDF downloads under a Creative Commons license.
- Convex Optimization – Stephen Boyd & Lieven Vandenberghe (PDF, no sign-up) – Cambridge University Press permits the authors to host the PDF for free.
- Open Data Structures – Pat Morin (HTML & PDF, no sign-up) – the book and source code are free (libre and gratis) under a Creative Commons license.
- Algorithms – Jeff Erickson (PDF, no sign-up) – this self-published textbook remains free; anyone may download, copy and redistribute it under a Creative Commons license.
- Think Python – Allen B. Downey (HTML & PDF, no sign-up) – a beginner-friendly Python book released under a Creative Commons license and explicitly described as a free book.
- Think Stats – Allen B. Downey (HTML & PDF, no sign-up) – the author’s site hosts a free, online version and encourages readers to share it under a Creative Commons license.
- Eloquent JavaScript – Marijn Haverbeke (HTML & PDF, no sign-up) – the fourth edition is available online under a Creative Commons Attribution–Noncommercial license.
- Dive Into Deep Learning – Aston Zhang, Zachary C. Lipton, Mu Li & Alex J. Smola (HTML & PDF, no sign-up) – this open-source interactive book offers free online and PDF versions.
- APEX Calculus – Gregory Hartman et al. (PDF, no sign-up) – an open-source calculus textbook; anyone can download and print the PDF version for free.
- OpenIntro Statistics – David M. Diez, Christopher D. Barr & Mine Çetinkaya-Rundel (PDF, no sign-up) – the OpenIntro collection notes that all its textbooks have free PDF versions.
- Introduction to Modern Statistics – Mine Çetinkaya-Rundel & Johanna Hardin (PDF, no sign-up) – an OpenIntro statistics text; the series offers free PDF downloads.
- Introductory Statistics for the Life and Biomedical Sciences – Nathaniel Horton & Benjamin S. Baumer (PDF, no sign-up) – another OpenIntro textbook with a freely downloadable PDF.
- Advanced High School Statistics – David M. Diez & Christopher D. Barr (PDF, no sign-up) – OpenIntro’s AP/advanced-high-school statistics book; the PDF is free.
- Introductory Statistics with Randomization & Simulation – David M. Diez, Christopher D. Barr & Mine Çetinkaya-Rundel (PDF, no sign-up) – part of OpenIntro’s free-PDF series.
OpenStax textbooks (free PDF & web view, no registration)
OpenStax, a nonprofit initiative at Rice University, publishes a wide range of peer-reviewed textbooks. Their policy explicitly states that the books are free to read online or download in PDF with no passwords or registration required. The following OpenStax titles are excellent resources:
- Calculus Volume 1 – Gilbert Strang et al. (PDF & Web, no sign-up) – first-semester calculus with interactive examples and problem sets.
- Calculus Volume 2 – Gilbert Strang et al. (PDF & Web, no sign-up) – covers sequences, series, and multivariable calculus.
- Calculus Volume 3 – Gilbert Strang et al. (PDF & Web, no sign-up) – advanced topics such as vector calculus and partial differential equations.
- University Physics Volume 1 – Samuel J. Ling, William Moebs & Jeff Sanny (PDF & Web, no sign-up) – covers mechanics and thermodynamics.
- University Physics Volume 2 – Samuel J. Ling, William Moebs & Jeff Sanny (PDF & Web, no sign-up) – electromagnetism and optics.
- University Physics Volume 3 – Samuel J. Ling, William Moebs & Jeff Sanny (PDF & Web, no sign-up) – modern physics and waves.
- Chemistry 2e – Paul Flowers et al. (PDF & Web, no sign-up) – a full general-chemistry text.
- Biology 2e – Mary Ann Clark et al. (PDF & Web, no sign-up) – comprehensive introductory biology.
- Microbiology – OpenStax (PDF & Web, no sign-up) – covers microbial structure, physiology and genetics.
- College Algebra – Jay Abramson (PDF & Web, no sign-up) – functions, polynomials and graphs for precalculus preparation.
- Linear Algebra – Jim Hefferon (PDF & Web, no sign-up) – a modern introduction to linear algebra and matrix theory.
- Differential Equations – William F. Trench (PDF & Web, no sign-up) – an OpenStax adaptation of Trench’s classic book.
- Principles of Macroeconomics 2e – OpenStax (PDF & Web, no sign-up) – macroeconomics with current policy examples.
- Principles of Microeconomics 2e – OpenStax (PDF & Web, no sign-up) – microeconomic theory and applications.
- Psychology 2e – OpenStax (PDF & Web, no sign-up) – foundational topics in psychology.
- Introduction to Sociology 3e – OpenStax (PDF & Web, no sign-up) – explores social institutions, culture, and modern issues.
- Biology for AP Courses – OpenStax (PDF & Web, no sign-up) – designed for advanced high-school or introductory university biology.
These books span mathematics, computer science, physics, statistics, economics and the life sciences. Because they carry open licenses and are distributed via trusted publishers such as MIT Press, Caltech, OpenIntro and OpenStax, they are excellent resources for self-learners and educators alike.
You may also be interested in my collection on free Artificial Intelligence books!