While happiness remains subjective, it certainly appears to be a buzzword in the popular consciousness right now. From Pharrell Williams' Oscar-nominated song, “Happy,” to a global day of recognition, happiness is all around.  

However, if you’re looking for something with a little more depth than just a catchy tune, here are five great books to pick up for International Day of Happiness, celebrated on March 20.

Related: Yes, You Can Be Happy While Pushing Yourself to Success

1. Flourish: A Visionary Understanding of Happiness and Well-being

Martin Seligman explores the depths of happiness in his recent book, Flourish. Seligman is the psychologist, author and TED speaker credited as the inventor of positive psychology and has long been a figure in the well-being movement. Martin argues that it’s up to us to flourish as individuals in order to create a happier society. He shares methods for improving your inner game with exercises such as how to practice kindness, express gratitude and focus your attention on your strengths rather than attacking your weaknesses. Packed with information and personal stories, Flourish can help give you the toolkit necessary for building everyday happiness.

2. The Happiness Hypothesis: Finding Modern Truth in Ancient Wisdom

Author Jonathan Haidt shares 10 theories of happiness discovered by the big thinkers of human history, such as Plato, Jesus and Buddha. This psychology professor weaves together a strong case for the similarity of all cultures' desires and pursuit of happiness. For example, literary giant Shakespeare says, “There is nothing either good or bad, but thinking makes it so,” which sounds remarkably similar to text from the Buddha, “Our life is the creation of our mind.” There is more in common than there is different in this study of happiness through the ages and around the world.

Related: Why Happiness is Your Secret to Productivity

3. Stumbling on Happiness

Daniel Gilbert’s book, Stumbling On Happiness, has been out for many years now but it remains a fascinating read. Another TED speaker, Gilbert is also a Harvard professor who has expertly managed to craft a case for happiness that even the most skeptic critic will take notes from. Perhaps the most unique aspect about Gilbert’s book is the incredibly dense research and scientific studies used to make the case for happiness. Yet like any great teacher, he manages to hand over all this data in a package that is easy to understand. His writing is accessible and can even be funny at times while discussing the mistakes we make in striving for happiness, yet poignant in pointing out that it’s human nature, which he backs up continually with research.

4. Happiness: A Guide to Developing Life’s Most Important Skill

Author, TED speaker and Buddhist Matthieu Ricard has a backstory that would make for a fascinating read by itself. The son of prominent French philosopher and intellectual, Ricard studied biochemistry, then decided to leave that life to convert to Buddhism. The result is a beautiful mind that weaves science, theory and philosophy into a study of the neurological effects of meditation and mindfulness training. Blending the wisdom of Buddhist practices with the most advanced neuroscience and latest psychology studies results in a book with brains and heart. Kind of like the perfect partner, Ricard’s Happiness is beautiful inside and out.

5. The How Of Happiness: A New Approach to Getting The Life You Want

Sonja Lyubomirsky is a University of California professor of psychology with the kind of extensive research background required to test and share insights into happiness. After her research on thousands of men and women, she has created a very detailed but simple case for how you can create happiness in your daily life. The How Of Happiness shares ways to pump up your joy in both the short and long term, as Lyubomirsky believes life should be enjoyed daily. She focuses on what happiness is and what you can do right now to experience it and sustain it for a fulfilling life with outlined strategies. You have to have a business plan to know where you’re going. It turns out, a happiness plan might be just as necessary.

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