Here are 3 relatively new Adobe resources for deep info about Adobe Digital Publishing Suite (DPS):
The newest resource is the Digital Publishing Suite Developer Center. This will be a home for more of the technical aspects of "pushing the envelope" of DPS.
Second, the Adobe Digital Publishing Suite Cookbook is a repository for tutorial-style "recipes" for creating different types of DPS content.
Third, check out the Adobe Design Center | Digital Publishing for designer-centric stories and tutorials about DPS.