mostly-adequate-guide

Which language(s) do you know already? If it's possible, have you looked at the state of FP in something you're already familiar with? For example, this guide in JavaScript is pretty good: https://github.com/MostlyAdequate/mostly-adequate-guide/ Or in Ruby, while you still have to create classes, you could explore writing pure functions and not changing state. Personally I feel like there's too many stumbling blocks in both those languages (unless you've got Lisp experience or are really into mathematics), and just getting used to the concepts in a more familiar environment will be more useful than scratching your head about monads.