Is there any book or online tutorial for Scala DSL?

I read this one for DSL scala http://camel.apache.org/scala-dsl-getting-started.html. It doesn't help much for me. I want more details. Can any one help me out?

Why is Scala good for DSL?

Scala is well known as a concise, readable programming language. One of the reasons is that many popular libraries offer their users DSLs to work with. These convenient APIs make creating programs simpler by saving our keystrokes and (most importantly) by improving readability.

What is DSL in Scala?

A Domain-Specific Language (DSL) is a programming language specialized in solving problems in a particular and finite domain. Internal DSLs are hosted and save us the need to write our tools to interpret the language. But the host language defines the limits of our DSL.

There is Debashish Gnosh book DSLs in action. It isn't focused entirely on Scala, but has a good section on DSL developemnt using Scala. Generally this would be enough for starter knowledge, for deeper experience I would look at either ScalaTest or Specs source code.