I've become a fan of the koans approach for learning the basics of new languages- basically, solve a bunch of little problems by making tests pass. Here are some for Scala- https://github.com/rubbish/scala-koans
Programing texts can usually only be so engaging. I have two books, 'Programming in Scala' and 'Scala for the Impatient'. Both good books, especially the second one if you are coming from a Java background and just want to get up to speed quickly.
Bot-war sounds like more fun though It would be nice to see more stuff like Rails for Zombies (http://railsforzombies.org/) for other programing languages .... especially for younger audiences.