3.0

The core ideas behind this book are interesting, but ultimately it failed to meet my (admittedly lofty) expectations. The framework Senge defines for creating/understanding learning organizations (using the five "disciplines") is thoughtful and coherent. He defines the five disciplines as:
1) Systems Thinking - Break free of linear cause-and-effect thinking and recognize the complex, interrelated forces at work. This is the "Fifth Discipline" referenced in the title, though Senge always discusses it first. I thought the book was going to spend a lot more time on this than it did.
2) Personal Mastery - Senge uses "Personal Mastery" to mean being committed to lifelong learning through reflection, patience, and working to see objective reality clearly.
3) Mental Models - Be explicit about your mental models (what are your assumptions? What is your understanding of the system at work?) and work to establish this as a cultural norm within your organization.
4) Building Shared Vision - Go beyond the fluffy vision statement, and describe "pictures of the future" that your organization can rally behind and strive toward. Profit or market dominance isn't a sustainable shared vision.
5) Team Learning - Use dialogue to communicate openly about all the disciplines above. Senge distinguishes between dialogue, or collectively getting at the truth, and discussion, or defending your point-of-view.

All of this seems to be genuinely good advice. I appreciated the overview of these topics, and the informal writing style the author used to describe what could have been a very dry subject. The author is thorough (more on this in the next paragraph), and the second appendix ("Systems Archetypes") is a useful overview of many common patterns in systems thinking.
My primary complaint about this book is a big one: it is that it needs a new editor. This is evident in small details (numerous typos and formatting issues, including all-caps, large type section headings that are misspelled) as well as in the organization and content of the book - it's waaaay too long for its content. The author repeats himself too much, and the stories used as examples can be rambling and redundant. The edition I have is the "revised and updated" version, and on the cover it says "revised and updated with 100 new pages." I don't know what the original edition was like, but I think perhaps they should have removed 100 pages when revising rather than adding.

If you're a reader with little or no background in systems thinking or reflective management, and are looking for a book explaining systems-oriented business management strategies, this might be a good introduction.