MongoDB: The Definitive Guide, by Kristina Chodorow, is a good introduction to MongoDB. It does not cover interacting with MongoDB in Scala at all, but Casbah is intuitive enough for anyone familiar with MongoDB.
Similarly, the MongoDB documentation (https://docs.mongodb.org/manual/) provides an in-depth discussion of MongoDB.
Casbah itself is well-documented (http://mongodb.github.io/casbah/3.0/). There is a Getting Started guide that is somewhat similar to this chapter and a complete reference guide that will fill in the gaps left by this chapter.
This gist, https://gist.github.com/switzer/4218526, implements type classes to serialize and deserialize objects in the domain model to DBObjects. The premise is a little different from the suggested usage of type classes in this chapter: we are converting from Scala types to AnyRef to be used as values in DBObject. However, the two approaches are complementary: one could imagine a set of type classes to convert from User or Repo to...
