Getting more focused on a particular subtopic seems to be a good way to get somewhat more advanced material. PragProg has a bunch of books for the Elixir ecosystem that might be up your alley (https://pragprog.com/titles/smgaelixir/genetic-algorithms-in..., for example).

I recently went through the Typescript resources over at https://executeprogram.com and found them really effective at solidifying the edges of that particular language for me; wish that was available for more ecosystems.