I use fp.ts quite a lot! I think it's _extremely unfortunate_ that the API docs don't include top-level examples for basically anything, though. So when people hit a problem that fp-ts or io-ts can solve, I have to basically write a disclaimer about the slight impenetrability before suggesting it.

I really think that TS itself should offer syntax more or less matching what that lib does at the type level, but this is a bit of a maximalist request.