It's true that it's one of the few books that's not about PHP code, but about the entire development life cycle. I owe a lot of thanks to Elizabeth Naramore and Marco Tabini of php|architect, for getting this book out. If you order the book, also check out its companion website. I will collect feedback on that site, and will regularly post errata or other updates.
Get more information (and grab yourself a copy) from the php|architect website - the print/PDF will cost about $30 CAD and the PDF only runs about $27 CAD.