Love the step by step approach connecting English and intuition to the more formal and theoretical stuff. Not ready to learn this stuff but Hindley-Milner is on my TODO list later. I can tell by first page that this will help a lot given the math looks like gibberish to me.

Note: Strange I did great in Algebra, Calculus, etc back in H.S. and college but proofs and such look gibberish. Maybe I should've taken a class with set theory or formal logic, eh? Paying for it now as I skim formal methods & FP papers...