is Max Euwe the most under appreciated champion

of all time

Max euwe was a fine chess player.

Absolutely! People always doubt the old amateur ;) He was seriously strong. He managed to defeat Alekhine. Alekhine was drinking, but he still played strong chess!

I've never heard anyone recommend the study of his games.

 Morphy, Lasker, Capablanca, Alekhine, Botvinnik, Petrosian, Rubinstein, Nimzowitsch, Fischer and many others, yes.

Euwe?  It's like he never existed.

Euwe was perhaps one of the best ( certainly most prolific ) writers on chess of all the world champions . I believe today he is known more for his writing/books on chess than for his play . 

Anything i've ever read by Euwe is very modest and humble. To have been a world chess champion and not be arrogant might be the most difficult feat possible for a chess player.