Introduction to Functional Programming (1988) [pdf]
Coming to FP very late in my career, I've never read this.  I've skimmed about half of it and it looks really nice.  Unless I'm mistaken, it appears that the entire book provides examples in pseudo-code which is pretty interesting.  I like their concept of specifications and the definition of strictness is really nice.  I'm looking forward to getting a bit of time to read it more fully.