What would you posit as required reading

for programming language design?

>>5-san has quite a wise recommendation. There're also:

Design Concepts in Programming Languages, which is quite a great and comprehensive tome. It also uses s-expression as a notation for AST.

I heard good things about Practical Foundations for Programming Languages , but haven't had a chance to look at it yet.

And what kind of /prog/rider that doesn't read SICP. There's also Essentials of Programming Languages while we're at that.

The dragon book is overrated. One can learn substantial compilation techniques from that though. I like Lisp In Small Pieces and Modern Compiler Implementation in ML better.