If you're into the idea, I'd recommend Purely Functional Data Structures by Okasaki and Pearls of Functional Algorithm Design by Bird, both really interesting books IMO.
Bird's book and its prequel, Thinking Functionally with Haskell, are outstanding.
His approach of calculating algorithms by performing algebraic transformations is very interesting.
It attracted some interest during the 80s and 90s, but it has faded away as it's too tough to be followed by a human. I wonder if it could benefit from some automation by using e.g. modern synthesis techniques.
