I have read several books /articles on A3 and this for me is the best so far.
The authors start by warning that the A3 report is just a tool, and that as with any tool, you need to know how to use it to get any real value from it.
They then run through the 3 standard types of A3 reports and the thinking behind each section in each of the related templates and how to use them.
They also lays out clearly how other techniques (Pareto / 5 Whys / Ishikawa) mesh with this, and the links back to Policy Deployment (Strategic imperatives).
The only negative for me was that most of the diagrams seem to be from manufacturing, whilst I work mainly with clients in the service sector.
Overall all though, really great.