I still have one of his books on the shelf "Foundation ActionScript Animation: Making Things Move!". Lots of great explainations on the math behind animation and its easy to ignore the Flash specific stuff.
Another good book (if that's still anyone's thing) on tweening is the freely available part Dynamic Visuals of Robert Penner's book Programming Macromedia Flash:
https://www.amazon.com.au/Foundation-ActionScript-Animation-...
Another good book (if that's still anyone's thing) on tweening is the freely available part Dynamic Visuals of Robert Penner's book Programming Macromedia Flash:
http://robertpenner.com/easing/penner_chapter7_tweening.pdf
http://robertpenner.com/easing/