At this time there is only one book covering Scala 2.12, and that is Programming in Scala, Third Edition by Odersky, Spoon, and Venners. It was released this past April. I have been running across recommendations for other Scala books and while those are good, this is the one book everyone who touches Scala must have. Even though I’ve referenced second edition numerous times, I bought third edition immediately and have been reading through it. I think I’m about half way through right now.