Scala books and resources
Functional Programming Principles in Scala at Coursera, a video course taught by Martin Odersky.
This is the best resource to get started in my opinion.
Functional Programming in Scala, Manning by Paul Chiusano and Rúnar Bjarnason
It is worth noting that the Scala standard library isn't implemented in a purely functional manner. This book is a workbook to learn functional programming in general. I have a dream that one day I'll complete this book. It does take time to go through all the exercises. It teaches functional programming the hard way. If this is interesting, you may want to check out the other libraries at typelevel.org which are fully functional implementations in Scala.
Programming in Scala by Martin Odersky, Lex Spoon, and Bill Venners
The first edition is available for free here. The 3rd edition of the book is current.
Beginner: (to be read in order)
Scala in Action by Nilanjan Ray Chaudhuri -- I've read only a chapter of this book, but I like the "in action" series, so this gets an honorable mention. At least the highlighted text boxes in the book are worth reading.
Scala Cookbook by Alvin Alexander, O'Reilly. -- I didn't read this book, but I've used the same content from his website http://alvinalexander.com/scala
Scala in Depth by Joshua Suereth
Programming Scala by Venkat Subramaniam is the fastest and most dangerous (may scare you away) way to get started in Scala. It was the first book I've read on Scala and I don't recommend it for the faint of heart.
Also take a look at this compilation of free Scala books.
The akka documentation is always the best and most current resource, but some books also help understand the paradigm. Read these books in order.
- Akka Concurrency by Derek Wyatt
- Effective Akka by Jamie Allen
- Reactive Messaging Patterns with the Actor Model by Vaughn Vernon
The creator of Akka, Jonas Boner has given some talks introducing akka, which can also be helpful.
The second course in the Coursera specialization in Scala also covers akka.