There are many reasons why I would recommend this book, too many to write here, but I'll try to be brief:
the writer's voice is so friendly and you can't help but feeling you're listening to a close friend giving you advice. The advice he gives is well organized in tiny chapters so you can always find your way around the book easily and look at what bit of advice you think will help you most. Also, each bit is independent, you don't need to take it in order.
The advice is all full of positive thinking, acceptance, tolerance, embracing reality and being proactive, taking initiative and not letting yourself get trapped into vicious circles of negative thinking.
The core lesson of the book is not taking your problems too seriously or blowing them out of proportion. I for one have a tendency to make a mountain out of a molehill, and this booklet helps putting things in perspective and deflating false fears.