The Implementation of Functional Programming Languages (1987). by SimonPeytonJones. A classic describing an implementation of MirandaLanguage (the predecessor to HaskellLanguage), and implementation of functional programming languages (pure ones which use GraphReduction, that is) in general.
Out of print; available online at http://research.microsoft.com/~simonpj/papers/slpj-book-1987/index.htm
Not to be confused with SPJ's other book ImplementingFunctionalLanguages
CategoryOnlineBook CategoryFunctionalProgramming