Unlike many other books written to assist thesis writing, this one is really worth buying. It is clearly written, has excellent ideas for organising your thesis (and indeed your entire phd/project), and has sensible suggestions about what should go into each chapter. The main difference between this book and others for phd students/report writers is that the ideas it contains are actually useful. I believe the book would be helpful to anyone writing any up any kind of project, not only postgraduate students.
Most of the suggestions are universally applicable, and I have found almost all ideas are helpful despite the general structure of my thesis differing a bit from those in the book. In particular, the book has had a big impact on my introductions and conclusions.
I had been completely stuck thinking that the task of writing my thesis was insurmountable when I finally got round to reading "How to Write a Better Thesis" and found inspiration. The examples help to maintain the book's relevance and "humanity", while the ideas on structure actually got me out of the quagmire I was in. Most other books contain a lot about presentation, whereas this one is more balanced, and actually gives you the tools to get started. It also helps you finish up with lots of handy checks to go through before handing in your final draft.
The first edition of the book also had chapters on writing reports and papers, and joint authorship, whereas the second edition has summaries at the end of each chapter and further material on going about research and dealing with your supervisor.