All these books are free to read: either they're distributed with a free license, or they're in the public domain.
The Docker and Kubernetes CI/CD eBook - Semaphore
Marko Anastasov, Jérôme Petazzoni, Pablo Tom F. Zavalia
Introduction to Philosophy: Logic
Bahram Assadian et al.
The Joy of Cryptography
Can Music Make You Sick?
Sally Anne Gross and George Musgrave
How To Code in Python 3
Open at the Margins
Taskeen Adam et al.
Survive the Drive
Tom Dingus and Mindy Buchanan-King
Abigail De Kosnik and Keith P. Feldman
An Atheists' Bible
Captain Quark and the Time Cheaters
Timothy McGettigan (editor) and William Shatspeare (Author)
The Internet Myth
2D Game Development: From Zero To Hero
Daniele Penazzo and 2DGD_F0TH contributors
Sight-Reading for Guitar
The Public Domain Song Anthology
David Berger and Chuck Israels
Economy, Society and Public Policy
The CORE Team
The Foundations of Hip-Hop Encyclopedia
Anthony Kwame Harrison and Craig E. Arthur, editors
The Impeachment Papers: A Compendium of Documents Related to the Impeachment of President Donald J. Trump