I come from an OOP background (Ruby!) and this is what I have done so far and highly recommend

That last one is an excellent look into functional programming

Check out my reviews in each of those threads for more of my thoughts on them too

I am currently reading…

And am loving it as well

Looking back at my own personal experience, I’m giving most of the credit to Clojure for busting my OO mindset. However knowing what I know now, I’d choose Racket instead (dealing with the JVM adds an unnecessary element of hassle - OK if you need it; otherwise avoid it). Some reasons for my opinion are detailed in these posts:

New to programming, how should I proceed in learning Elixir? - #18 by peerreynders

Will reading a Haskell book help adopt a functional programming mindset? - #9 by peerreynders

Opinions on Elixir vs. Clojure - #16 by peerreynders

One potential starting point is Realm of Racket as HtDP2e may feel a bit slow for an experienced programmer and SICP with DrRacket may be a bit academic (though Peter Norvig’s Amazon review is an entertaining read).

Then “practice” with something like exercism.io.

Once you feel that Racket has put a big enough dent in your OO mindset double back to Elixir with

Learn Functional Programming with Elixir (Pragprog)

at which point you should be much less tempted to approach Elixir in imperative/OO ways.

PS: Of course, you can try the pure Elixir path as already suggested - but I find that often a well established OO mindset needs to be approached with the equivalent of a baseball bat.

Seems like you are just about ripe to branch out into F#.

True story →

I’m sure most people here are too young to remember Jerry Pournelle. He was a science fiction author who wrote a column for Byte magazine for many years about his tinkering with computers. In my opinion, they started out as reasonable accounts of exploration by a hobbyist. But over the years they somehow morphed into an almost-knows-nothing guy annoyingly pretending to be an expert (boring accounts of tortuous feats of kludgery to avoid new-fangled tech).

Anyway, after the publication of SICP, there was a corkboard outside Sussman & Abelson’s offices covered with reviews of the book. In a place of honor, dead center with some space around it, was Pournelle’s review which stated “I didn’t understand a word of it.”

This might be for you: https://fsharpforfunandprofit.com. Aside from anything else, Scott Wlashin’s site has some excellent material on functional programming in general.