This a good read. I like the railway analogy. "Functional Programming in Scala" is also well worth a read as well if you're trying to learn FP... I've found it

This a good read. I like the railway analogy. "Functional Programming in Scala" is also well worth a read as well if you're trying to learn FP... I've found it to be excellent, especially since it has lots of exercises to use for practice.