Haskell is a general purpose, purely functional programming language. Haskell compilers are freely available for almost any computer. This store sells books about or relating to haskell and functional programming.

Implementing Functional Languages: a tutorial (Paperback) $18.50	Type Theory and Functional Programming (Paperback) $18.50	Optimization for Lazy Functional Languages (Paperback) $18.50
Haskell Foreign Function Interface (Paperback) $7.00