I tried to follow the suggestions in this book. First of all, if you really want to use this as a how-to guide, its format is not conducive to that. The very few specific actions it recommends are buried in text that is full of anecdotes and studies that are supposed to sell you on the thought that doing these actions will make you happy. Also, according to the author the solution to all of your problems seems to be writing in journals: your "Best Possible Selves" journal in which you are trying to cultivate optimism by imagining what your life will be like one it is exactly the way you want it to be, your "Goals and Subgoals Journal," your "Trauma" journal, in which you write about traumatic experiences you've had as a way of coping with stress, a "Gratitude journal" in which you are writing what you are grateful for, etc etc etc. While I can see how writing can help people become more optimistic and grateful, lighter in spirit and more focused, the author does not give specific advice on what questions to ponder while writing.
I felt after reading this book (several times) that it was a less helpful, more commercialized version of a much better, more helpful and more specific book which was written several years ago, "The Emotional Toolkit" by Darlene Minnini (also a PhD from California, although from UCLA). The Emotional Toolkit cites the same studies that The How of Happiness cites and more, but is more focused on the reader and what he or she can do, not exclusively on selling the idea of what they should do. It gives specific suggestions, which How does not; such as listing questions to ask yourself while writing in a journal, for example, and questions to ask yourself to shift your thoughts from negative to neutral (instead of How's simply telling you to "stop" the negative thoughts because negative thoughts are bad for you).
So, if you really want to help yourself, I would not go for How of Happiness.