It's definitely not the kind of language that you spend a few weeks or months with to learn a few new concepts. It's a language you learn because you can see yourself doing a lot of real programming in it. I call it the C++ of the Java world, meaning that Scala is to Java as C++ is to C: a more complex and expressive language that piggybacks on top of a hugely successful ecosystem and is a powerful tool for those who invest the time to learn it well. I'm learning it because I think it has a bright future in commercial software development, and it's nicer to work with than most languages that can say that.

It struck me the other day that I would love a "Scala: The Good Parts". Wouldn't it be great if there was a small, powerful kernel in there, somewhere, and someone explained it...

Even if there were such a book, you'd have to deal with other people's code that used the "Bad Parts" of Scala. I dread deciphering clever Scala one-liners.

While definitely not small, the stairway book, "Programming in Scala" by Odersky, mentioned in the article, is an excellent tutorial style book. The second edition was just released in January.