The Routledge volume Researching Non-State Actors in International Security: Theory and Practice, edited by Andreas Kruck and Andrea Schneiker, has now been turned into a fully open access book. The book contains chapters on “interpreting texts” (Part I), “establishing causal claims” (Part II), and “doing fieldwork” (Part III). I contributed a chapter on “Qualitative Comparative Analysis and the Study of Non-State Actors” to Part II of the volume. The book’s substantive chapters are complemented by “discussion chapters” where commentators draw together and reflect upon the respective areas of research. Many thanks to the editors and other contributors for their efforts turning this into an open access book! I am grateful for the open access funding approved by the University of Erfurt to contribute to this aim.