The folks at Technology for Publishing have created a really nice "how-to" book about the Adobe Digital Publishing Suite (DPS). The book is titled DPSCreate™: Building Interactive Content. It can be purchased in downloadable form as a PDF or in a printed version. This clear, concise, accurate handbook is a nice guide to learning how to use DPS, as well as a handy reference manual.
The book starts out with an overview of terminology and the DPS process, discusses recommended file and folder structure, and recommends how to start building DPS files. Then the bulk of the book is spent on how to create the various types of interactive content that can be added to DPS apps.
The content of the book is also available as an iPad app.
If you are learning DPS, you need to buy either the app or the book!