Textbook in PDF format This volume presents cutting-edge research on one of modern cosmology's most intriguing challenges: the observed dipolar anisotropies that appear to conflict with the standard ΛCDM cosmological model. Through its contributed chapters, the book extensively examines multiple lines of evidence suggesting directional preferences in various cosmological observations, from cosmic expansion to galaxy cluster distributions. The work explores two fundamental possibilities: either these dipoles represent genuine spacetime anisotropy, challenging the cosmological principle itself, or they indicate a need to revise our interpretation of the cosmological data and the current models of large-scale structure formation. Both scenarios carry profound implications for our understanding of the universe's fundamental nature and evolution