There are huge lists on freely available books on programming topics here (most would probably not fit your 3rd point though):
* https://ebookfoundation.github.io/free-programming-books/boo...
* https://ebookfoundation.github.io/free-programming-books/boo...
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All my books are free to read online and markdown sources are available on GitHub: https://github.com/learnbyexample/scripting_course#ebooks