Textbooks: How to Think Like a Computer Scientist: Python-3 and C# versions.
These free open-source textbooks were developed and used with an introductory Computer Science course over some years.
Sources for both books uses reStructuredText markup which is then processed by Sphinx.
The html is not easily viewable directly on github, so the output has been zipped up. You can download and unzip it for convenient viewing without having to process and build the source yourself.
thinkcspy3.zip for the Python-3 book. ThinkSharply.zip for the C# book.
Enjoy!
Peter Wentworth