If you need the sequence diagrams, probably you could take the source codes and reverse engineer from them. The big picture, however, does give you the understanding of how the request and response flows.
There is a high level request walk-through description here. [ April 29, 2008: Message edited by: Chengwei Lee ]
We don't provide UML digrams in the book. But I assure you that we explain a lot more of the details about how the component of the architecture actually work and communicate together than most tech books. For instance, we spend a lot of time explaining how the interceptor cooperates with the action, and how the entire processing sequence, an action invocation, gets initiated and managed. This is pretty detailed stuff.