Leadership theories have evolved over the decades, reflecting its complex and multifaceted nature. This narrative literature review aims to analyze significant leadership literature in popular leadership course books and published peer-reviewed English articles, from which future research directions can be extrapolated. Various development stages of leadership, which hold different research values, are examined and discussed. Since some emerging theories appear to be understudied (shared/distributive leadership, complexity theory of leadership, etc.), there are arguably much scope and opportunities for these to be developed in the future.