Flow: The Psychology of Optimal Experience
This book by Mihaly Csikszentmihalyi started an entirely new field of research, and defined many terms that you’ve probably heard, but perhaps don’t fully understand.
Most of us would choose play time over work time, and that’s often the wrong choice if we value our happiness… facing challenges well matched to our skills gives us the opportunities to learn and grow that are essential to happiness. When we choose leisure activities that are essentially passive we lose these opportunities for growth and happiness.
If you aren’t fully satisfied in any facet of your life (and especially in your work) you need to read this book.