Sonja Lyubomirsky has been conducting research in the science of happiness for 18 years and has seen it expand as part of a movement called positive psychology. This engaging resource starts with a short diagnostic quiz which enables readers to identify their "happiness set point." Lyubomirsky reveals that 40 percent of our capacity for happiness is within our power to change through the ways we act and think. Backed by research conducted with thousands of men and women, the author presents a theory of determinants of happiness and the best strategies to bring about a life of contentment and fulfillment.

In the United Sates, Greece, Slovenia, South Korea, Argentina and other nations, when asked what they want most in life, people put happiness at the top of the list. Lyubomirsky defines this elusive quality as "the experience of joy, contentment, or positive well-being, combined with a sense that one's life is good, meaningful, and worthwhile."

The author debunks three myths about happiness: 1. Happiness Must Be "Found." 2. Happiness Lies in Changing Our Circumstances, and 3. You Either Have It or You Don't. She concludes that "the fountain of happiness can be found in how you behave, what you think, and what goals you set every day of your life."

The second section of the book contains 12 happiness-enhancing strategies and five important hows behind abiding happiness. Among the happiness activities are:

• Expressing Gratitude
• Cultivating Optimism
• Avoiding Overthinking and Social Competition
• Practicing Acts of Kindness
• Learning to Forgive
• Savoring Life's Joys
• Taking Care of Your Body

Lyubominsky, who won the 2002 Templeton Positive Psychology Prize, makes a good case for practicing optimism and putting others ahead of ourselves. There is also plenty of helpful material here on depression and other obstacles to being happy.