This book discusses Mobile Libraries, a kind of Libraries that has mainly existed and operated in close proximity to the everyday lives of simple people. Using the term simple people we mean those who are not necessarily engaged in professions related to science and, in any case, not occupied in the academic field. Thus, in our effort to analyse the intensely social role of Mobile Libraries, we have adopted an approach that also uses some theoretical concepts and "tools", which primarily originate from social sciences - therefore expresses a sociological perception. Hence, our perspective is interdisciplinary, since it is also Historical, given that we have dedicated a separate chapter of our book to the History of those Libraries. Note, finally, that we have often adopted the comparative method, which is considered appropriate in all social sciences, as we compare the operation of Mobile Libraries to the operation of other, "conventional", as we call them, Libraries - e.g. Municipal and School libraries.