“The book offers a wonderful overview, very well structured and complete, on the theory of harmonic analysis developed in the context of the Vilenkin-Fourier series. … each chapter begins with a broad introduction rich in bibliographical citations that allow the reader to locate himself in the historical context of the topics to be addressed … the authors include an important and interesting list of open problems proposed with a view to being resolved in future research.” (Iris Athamaica López Palacios, zbMATH 1512.42042, 2023)