I recently found this talk: http://www.confreaks.com/videos/1287-rubyconf2012-y-not-adventures-in-functional-programming http://www.confreaks.com/videos/1287-ru

I recently found this talk: http://www.confreaks.com/videos/1287-rubyconf2012-y-not-adventures-in-functional-programming http://www.confreaks.com/videos/1287-rubyconf2012-y-not-adve... which I think it's a good introductory material: it not only derives Y, but starts with introducing all the tools needed for the derivation and explains rationale for using given tool at every step of derivation. Nice, however rather long. Personally I found "The Little Schemer" explanation the first that made it click for me. Its unique style of making you do the exercises even if you don't do them (it's hard to explain, just go and read the book) gives you an impression that you really understand what is happening.