Haskell and ML languages look like symbol soup when you're used to mainstream/C style languages. Once you understand some of the basic syntax they become quite readable and easy to reason about as a series of transformations.
Step one, which applies to most functional languages, is knowing how to read a Hindley-Milner type signature [1].
Armed with that you can often gain a surface level understanding of what some function does - and what the program does in aggregate - just by reading type signatures and seeing what calls what.
Hoogle [2] is a good resource for figuring out Haskell syntax, like what's up with all of those $ signs.
Converting OCaml to ReasonML syntax with sketch or reason-tools [3] makes OCaml less foreign.
With basic knowledge of Haskell and ML syntax you'll find many FP languages readable.
[1] https://drboolean.gitbooks.io/mostly-adequate-guide-old/cont...