Mauricio, as the book is developer's guide so I think it should be more from technical perspective. Mainly to illustrate:
- BAM - how to access history information (what was already executed even if the process instance is not finished yet).
- Tooling - dynamicity and versioning when using Guvnor/Designer and jBPM console
- Tooling - new features of designer - generate forms (maybe even form builder), service repository import
Does that sound suitable for the book?
Cheers