This paper tackles the issues of overlay publications (journals, but also edited monographs and books in general). Its two parts are aimed at providing theoretical understanding of what an overlay publication is and at examining a concrete example of a print on demand overlay book, published after the free digital version was released. The first part takes into account the definitions found in literature and goes back to the functions that every system of scholarly publication must satisfy, as Roosendaal and Geurts (1997) proposed, adopting a value chain perspective of the scholarly communication system. Some examples of overlay journals are then examined in order to clarify which added value an overlay publication can contribute. According to the first part, the second part of the paper analyzes in depth a first experiment of what can be defined as an overlay book. The case study is about a short monograph in Italian, in the field of online and social marketing published first as a free ebook and then published in print through a print on demand model. The paper ends summarizing the findings of the case study and providing some insights about overlay publications, trying to clarify what they are and why they are useful.