Flow by Mihaily Cszkizentmihalyi is an essential read for anyone studying flow and world-class performers. This classic on the subject is the layman’s terms version of the decades of research that Cszikzentmihalyi did on studying and coining the term of flow state. 

This book goes on a deep dive through the subject of happiness and optimal experience which is usually how flow gets defined. 

It starts by exploring happiness and how we consciously process the state of happiness and then digs deeper into the state of flow and how it gets produced through various activities. 

Ultimately flow requires a challenge be pushed to the limits of the individuals capabilities. Whether it is assembling widgets in a factory and striving to constantly do it a little faster, or free soloing a rock wall that has never been done before. Just about any activity or job can become flow-producing when the right conditions are met.