As a Scala instructor, I often get asked about books for learning the language at different levels of expertise.

This is my attempt to summarize the best books out there.

Please, if you spot any omissions or inaccuracies, let me know.

Disclaimers

I have read some books thoroughly, but not all. Some I have evaluated with a rather fast scanning.
I have no intention to diminish the work of any of the book authors. Putting a book together is a tremendous endeavour, and I'm very thankful for all the work they've done.

About the table below

I've classified books based on their target experience level, as such:

Beginner books, in green, require little related experience.
Intermediate books, in yellow, expect some level of knowledge in related technologies.

What about the other tags I've included?

Hands-on: Does the book provide code samples and exercises for the reader? (Minimal, Somewhat, Very)
Reference: Is this a good book to keep as reference material once you're somewhat comfortable and are starting to do real work with the language?
FP ↔ OO: Where does this book fall in the Functional-Programming to Object-Oriented continuum? FP means the book is focuses on how to write code in Scala that meets the Functional Programming principles. OO means functions have a relatively short treatment and Functional Programming does not permeate most of the book. Hybrid means somewhere in between.

The books

    

    
        
            Title
            Authors
            Year
            Hands-on
            Reference
            FP ↔ OO
        


        
            Atomic Scala
            Bruce Eckel, Dianne Marsh
            2015
            Very
            No
            OO
        

            Beginning Scala 
            Vishal Layka, David Pollak
            2015
            Minimal
            No
            Hybrid
        

            Scala for Java Developers
            Thomas Alexandre
            2014
            Somewhat
            No
            OO
        

            Functional Programming in Scala
            Paul Chiusano, Rúnar Bjarnason
            2014
            Very
            No
            FP
        

            Learning Scala
            Jason Swartz
            2014
            Somewhat
            Maybe
            Hybrid
        

            Programming in Scala
            Martin Odersky, Lex Spoon, Bill Venners
            2016
            Somewhat
            Yes
            Hybrid
        

            Scala in Action
            Nilanjan Raychaudhuri
            2013
            Minimal
            No
            Hybrid
        

            Scala in Depth
            Joshua D. Suereth
            2012
            Minimal
            No
            Hybrid
        

            Scala Cookbook
            Alvin Alexander
            2013
            Very
            Maybe
            OO
        

            Programming Scala
            Dean Wampler, Alex Payne
            2014
            Somewhat
            Maybe
            Hybrid
        

            Scala for the Impatient
            Cay S. Horstmann
            2016
            Somewhat
            Maybe
            Hybrid
        

Title	Authors	Year	Hands-on	Reference	FP ↔ OO
Atomic Scala	Bruce Eckel, Dianne Marsh	2015	Very	No	OO
Beginning Scala	Vishal Layka, David Pollak	2015	Minimal	No	Hybrid
Scala for Java Developers	Thomas Alexandre	2014	Somewhat	No	OO
Functional Programming in Scala	Paul Chiusano, Rúnar Bjarnason	2014	Very	No	FP
Learning Scala	Jason Swartz	2014	Somewhat	Maybe	Hybrid
Programming in Scala	Martin Odersky, Lex Spoon, Bill Venners	2016	Somewhat	Yes	Hybrid
Scala in Action	Nilanjan Raychaudhuri	2013	Minimal	No	Hybrid
Scala in Depth	Joshua D. Suereth	2012	Minimal	No	Hybrid
Scala Cookbook	Alvin Alexander	2013	Very	Maybe	OO
Programming Scala	Dean Wampler, Alex Payne	2014	Somewhat	Maybe	Hybrid
Scala for the Impatient	Cay S. Horstmann	2016	Somewhat	Maybe	Hybrid

A few words about each book

Atomic Scala: Very well structured book, carefully thought out. I love the small exercises. It's unique among this list in that it target readers with little or no programming background! Great as an introduction. Focuses on the language features, not on the patterns that arise with its usage. Barely mentions Functional Programming.
Beginning Scala is clearly tailored to inexperienced developers, and provides a somewhat practical approach. Several advanced topics are missing, but that's expected for a book with this focus.
Functional Programming in Scala is a fabulous book, alas not an easy read. It's clearly written with Functional Programming at its core, and it will challenge the reader to solve many non-trivial exercises. Even for some of us who don't necessarily want to be FP purists, this book is an amazing experience.
Learning Scala is a well written book, that provides a good introduction to the language. It provides, however, less exercises than I would like.
Programming in Scala is clearly a must-have. Written by the creator of the language and two tremendously experienced developers. Very thorough, and a great book to have as a reference. It provides many small examples as you progress. Sadly, as is the case with most books, it provides no additional exercises for the reader to practice and deepen her understanding.
Programming Scala stands out as a book for developers that have related experience. It provides very valuable patterns and practices, and goes beyond the language and into other valuable tools, such as Actors, IDEs, build tools, and several others.
Scala Cookbook is a very practical and useful list of recipes - small problems solved using Scala. Despite it being almost 3 years at the time of writing this, it's not showing its age much just yet.
Scala for Java Developers focuses on a very practical use - how to write a Web application backed by a Database while using Scala. It's not a great alternative for learning the language itself.
Scala for the Impatient focuses on being very practical from the very beginning, and it does a very good job at it. It provides small exercises as you progress, and you find yourself playing with the language from very early on.
Scala in Action is a solid book, but its age is starting to show, which concerns me. It focuses less on learning the language, and more on how to build an application with it.
Scala in Depth is another great book that is starting to show some wrinkles after a few years of its last edition. Would be great to have an updated edition.

So, what do I recommend?

If you want to learn the language, I recommend this combination (in this order):

Atomic Scala as an introduction, and to get you warmed up.
Programming in Scala to fill some gaps and to always keep around for later reference.
Functional Programming in Scala to build (or strengthen) your FP muscles and start your journey into this wonderful (but not always easy) path.