Atomic Scala by Bruce Eckel and Dianne Marsh.
From the webpage:
Atomic Scala is meant to be your first Scala book, not your last. We show you enough to become familiar and comfortable with the language — competent, but not expert. You’ll be able to write useful Scala code, but you won’t necessarily be able to read all the Scala code you encounter.
When you’re done, you’ll be ready for more complex Scala books, several of which we recommend at the end of this book.
…
The first 25% of the book is available for download.
Take a peek at the “about” page if the author names sound familiar. 😉
I first saw this at Christopher Lalanne’s A bag of tweets / August 2012.