After watching the documentary, I wasn't entirely sure I wanted to buy the book. The documentary came across as a bit whiny, and focused a lot on No Impact Man's wife and her reluctance to certain parts of the project. However, I am very glad I bought the book. It is brilliant and I'd recommend it to everyone, hence the five stars.
One drawback I would like to mention is that the book still doesn't go in enough detail for me. At the beginning of the appendices, there are about 15 links to blog posts you can read for more info. I fail to understand why these weren't included in the book, considering it is actually a much shorter book than you'd think. An entire 15% of the book consists of appendices, references and acknowledgements. A further 25% of the book is an index, which incomprehensibly is placed at the back and is a bit pointless in a Kindle version (you can just use the X-Ray function). My copy cost £4.99 from Amazon.co.uk. I normally make a point of never buying an e-book for more than £4 so I put it on my wishlist and waited. And waited. And ran out of patience, which sadly is not one of my virtues, and bought it anyway. The book was listed as having 282 pages, but as you will only really read about 60% of those, I effectively paid nearly £5 for roughly 170 pages.
I still think the book is worth it, and I will probably open the Kindle app on my Mac and check out all those blog post links, but I just wanted to make any potential buyers aware of the above.