It's not highlighting one thing, but Chris Okasaki's book on Purely Functional Data Structures, and this brilliant top answer to a question about functional dat

It's not highlighting one thing, but Chris Okasaki's book on Purely Functional Data Structures, and this brilliant top answer to a question about functional data structures published since the book will keep you in reading material for a while: http://cstheory.stackexchange.com/a/1550 http://cstheory.stackexchange.com/a/1550 (it was all 'lesser known' to me when I started using haskell not so long ago)