This is a difficult book to review objectively - like alot of self help books, whether or not the reader will find it helpful is completely subjective.
As obectively as I can be - this ebook is formatted well and was very easy to read. I read it cover to cover in about an hour and 1/2 so if you want either a "quick read" rather than anything too deep and meaningful, or haven't read any other books on the subject before, this may be a good one to start with. If you have read quite alot on the subject already, this book may also be useful to act as a reminder of some of the basic principles of finding happiness. Each of the 18 rules are discussed in individual chapters making it easy to refer back to paricular points at a later date if you want to.
The down side is that each subject is not discussed in any detail and whilst the the author does give suggestions on things you can actually do to find happiness - go out with friends more often, take up a new hobby etc.. he does not acknowledge such changes are not always that easy to do. The author also fails to discuss the changes in perception the reader needs to make both of self and the world around them in order to put each rule into practice in the first place. He does say throughout the book that we need to change how we think about things but does not discuss "how" to change our thinking
I personally did not find this book helpful although persevered to the end. There are alot of books out there which are far more thought provoking and if you've read any of them and been inspired to read more, this book probably isn't for you.
Overall, I did not find this book helped me personally but looking at the reviews, other readers have the opposite to be the case. My advice would therefore be to have a read through all the reviews and if you're still not sure whether or not it's for you, it only costs 49p to download so try it for yourself and see what you think.