Can anyone recommend good books on game design?

This is an interesting book series that is still in development: https://leanpub.com/b/development-and-deployment-of-multipla...

“Designing Virtual Worlds” by Richard A. Bartle.

Awesome site by the author (a legend) where you can download the PDF: https://mud.co.uk/dvw/.

A good place to start: The Art of Game Design By Jesse Schell.

https://www.schellgames.com/art-of-game-design/