Dr. Richard Schonberger has published this year (2008), his latest review of Lean proficiency. The link in this blog takes you to the UK Amazon page should you wish to buy it.
The publication draws heavily on Richard Schonberger's excellent and growing database of Companies' Lean practices. The book uses the data to draw messages and conclusions on the adoption, and retention of Lean practice. While weighted in this data, the author manages to take a balanced and incisive discussion without overwhelming the reader. I recommend this to any involved in the development or pursuit of Operational and Manufacturing excellence.