(this may be daunting; if one's not reasonably versed in haskell basics, read last 5 chapters of

http://learnyouahaskell.com/chapters

I did read http://learnyouahaskell.com/functors-applicative-functors-an... and found myself unsure if I had understood anything at all. (Not a reflection of this book - which I do agree is fabolous.) And now am reading both (last 5 chapters) and this wiki in tandem.