The service system has been proposed as the basic abstraction of service science and, as a result, there has been much interest in the study and analysis of service systems in recent years. This paper presents the results of a systematic literature review of recent literature on service systems through which we characterize recent changes in direction and focus in service system research and identify new emphases and areas of focus. We discuss three approaches to service system analysis: descriptive, prescriptive, and evaluative. We also discuss new research focused on studying the components of service systems. Based on research gaps observed in our review, we identify eight specific opportunities and three broad directions for future research: (1) refocusing attention on a greater diversity of research designs and analytical approaches, (2) leveraging new perspectives to perform more ontological work on system components, and (3) fostering a better understanding of the role of innovation. We present a framework of our key findings, depicting the overarching logic linking research questions, opportunities, and directions.