Functional Programming in Scala

Not-technical "The World's Toughest Endurance Challenges" - Very nicely illustrated "Thing Explainer: Complicated Stuff in Simple Words" - Extremely enjoyable. People here certainly are aware of xkcd and it's type of humor. Technical "Functional programming in Scala" - good read for Scala beginners, especially after "Scala for the Impatient" "Learning Spark" - the best book on Spark so far "Assessing and Improving Prediction and Classification" - couple of interesting ideas for ML and Data Science "Neural Network Design" - Quite basic, but I like the flow and introducing mathematical concepts just before they're needed.

Programming Scala 2nd edition and Functional Programming in Scala.

Functional Programing in Scala (http://www.manning.com/bjarnason/) More recent than most books mentioned here, but I found it remarkably well-written. Irrespective of what happens to Scala, this book has a good chance to be useful 10 years from now.

Functional Programming in Scala. It's not a book about scala, it just so happens to use scala as the language to teach you how to program functionally. I've read other books that purport to do the same, they end up showing a light sprinkling of functional concepts. This book goes much deeper, and is ultimately much more rewarding.