What would be a good book / website to learn the concepts & nomenclature in order to understand the advanced language discussions in HN like this one?
(I also own & admire his Basic Category Theory for Computer Scientists; I'm yet to brave his Advanced Topics in TaPL - I'm sure it's very good, but the contents list intimidates me.)
For type systems your best bet is to learn languages with advanced typing features. Start with the friendly ones (TypeScript, python mypy, Rust, Haskell) and look at Idris for dependent types.
And then reread this post, and ask a lot of questions (reddit, stackexchange, quora).