Ciro Santilli Very good open source book: github.com/csound-flossmanual/csound-floss
Includes introduction to the basic sound synthesis and their implementation in Csound.
Examples run on browser via Emscripten and just worked on Ubuntu 20.04!
Examples can also be downloaded all at once from: www.csound-tutorial.net/floss_manual/ Shame not in Git as standalone files.