In a word, brilliant. I scanned through Head First EJB about a year ago and was extremely impressed by their fresh approach. They categorically state there will be plenty of redundancy, and redundancy is exactly what people need to learn tough concepts. So, within a chapter on a particular topic, they’ll jump between various formats - normal prose, Q&A, diagrams, stories. And the best format of all: cartoons showing EJBs chatting, and sometimes arguing, with each other (a little like this TSS cartoon, Dion).
People like to anthropomorphise technical components, so it can be a very powerful learning tool to show EJBs arguing about who does what. The redundancy is the key here: combine such evocative imagery with more detailed tech talk, and you have a format that keeps readers motivated and answers many more questions than a standard prose form would.
I’ve tried to do something similar to this with the Metaphors for the Gang Of Four Design Patterns. It’s a completely different way to describe patterns, and I think that people can learn patterns best by seeing how they apply in as many contexts as possible.