Seconding a comment on the linked url, but adding the url, for the lazy amongst us :

lambda papers (steele, sussman) http://library.readscheme.org/page1.html

and btw, an interview of john backus : http://archive.computerhistory.org/resources/access/text/Ora...

discussing amongst other things, the pros/cons of fp, and his issues solving how to fit IO; not mandatory but highly refreshing.