Scala is an exciting, modern, multi-paradigm language for the JVM. You can use it to write traditional, imperative, object-oriented code. But you can also leverage its higher level of abstraction to take full advantage of modern, multicore systems. Programming Scala will show you how to use this powerful functional programming language to create highly scalable, highly concurrent applications on the Java Platform.
That sounds like the domain of scientific computing. To contrast, Programming in Scala has a more general focus, as its title would suggest.