The book "Unveiling the Globular Cluster Systems of Early-Type Galaxies" offers a comprehensive investigation of the globular cluster (GC) systems in early-type galaxies (ETGs). By analyzing extensive image data collected from renowned telescopes such as the Subaru Telescope, the Canada-France-Hawaii Telescope, and the Hubble Space Telescope, the evolutionary history of these galaxies is illuminated. The work also includes spectroscopic data obtained from the Keck II Telescope to determine the characteristics of the GC systems in five specific ETGs. The results reveal interesting correlations between the properties of the GC systems and the environmental conditions of the galaxies, providing new insights into the dynamics and evolution of these astronomical objects.