As an IT trainer for PDF and prepress, I have found this book to be invaluable.
If you're trying to make sense of the PDF workflow, this is one of the best books you can get. It covers different ways of creating PDFs (export, distill etc) in great detail, looks at collaboration and proofing, and goes into thorough detail on workflows and Extreme technologies. Even leafing through it should allow you to approach PDF workflows with greater confidence.
Future editions might benefit from a look at using LaserWriter instead of Adobe PS for writing PostScript and PDF (there is an overall bias towards Adobe and away from Quark in the book), getting good PostScript out of Mac OSX (maybe Acrobat 6 will remedy this) and the inclusion of a real life example with settings etc. This might help to make better sense of Color Management in PDF. Also, there is no accompanying CD or web site yet.