Leaving aside the question of whether LEAN is the answer to the world's problems, or just the next management fad, my opinion of this book is heavily dependent upon what I think it is supposed to accomplish. I believe it is mediocre at being a narrative overview of what LEAN is all about, but that it fails miserably as any sort of guide or reference book. Since the title is "LEAN for Dummies", I guess it is only fair to rate it as a narrative overview. More experienced readers will tire of the "wordy" format, opinions and lack of summaries and easy references.
Some sections of the book are quite good. The summary and descriptions of the types of waste (Muda, Mura and Muri) are first rate, with reasonable examples of each. Further, there is a nice table summary of the 7 types of Muda, and even a brief description of type 1 versus type 2 muda (stuff that you really can't eliminate versus stuff you can). In short, this section is what I believe the book should be about. Three pages that you can read in about two minutes, and have an appreciation for the concept. No one will ever confuse you with an expert, but you won't embarrass yourself either.
Other section of the book border on horrible. Control charts, one of the most common features of a LEAN implementation, are skipped over in a page or two. There is an example chart, and a statement "Typically, as long as the sample values fall between the upper and lower control limits, the process is 'in control'. However, if the distribution is systematic and non-random, this is an indication of special causes..."
No idea what you are supposed to make of that statement. Nor is there any hint as to how to calculate upper and lower control limits, or even x-bar. A check of the index indicates no hits for CpK or process capability calculations.
Finally, there is a lot of "soapboxing" scattered throughout the text. I could point to numerous examples discussing government, quality control, complacent managers, but here is one example (p 109). "One mistake companies frequently make ... is failing to recognize the strengths of a company being acquired. Learn from the new organization. Don't assume they don't have anything to offer..."
That may be good advice, it may even be true. But it has little, if anything at all, to do with LEAN. Indeed, if were were to follow the tenets of LEAN, we would strike this whole section from the text as a form of waste.
In summary, I would say the book is great if you work for a company that has or is starting a LEAN implementation, and you want to at least know what everyone is talking about. If you are in anyway involved in the implementation, especially if any statistical control is involved, you will need a much more comprehensive and instructional book.