"The Universe of Digital Sky Surveys" is a comprehensive collection of contributions published in honor of Massimo Capaccioli's 70th birthday. These proceedings provide an overview of the most significant current and past digital sky observation projects and their impact on astronomy. In recent decades, digital sky surveys conducted with specialized telescopes and advanced wide-field cameras have revolutionized astronomy. They have become an indispensable tool for exploring the near and distant universe, yielding new insights into the structure and formation of galaxies, the dark components of the universe, and the history of our own galaxy. Furthermore, these surveys have expanded the understanding of transient phenomena in the universe and facilitated access to high-quality data for astronomers, reducing their reliance on large observational facilities. The various sections of the book address different relevant aspects of astrophysics in the era of digital sky surveys and include both comprehensive and focused contributions.