This article describes the results of a systematic review of peer-reviewed, published research articles about "discovery layers," user-friendly interfaces or systems that provide single-search box access to library content. Focusing on articles in LISTA published 2009-2013, a set of 80 articles was coded for community of users, journal type, research method, and results. The findings suggest sustained and potentially a converging professional interest in discovery layers over time. They also demonstrate what has not been studied, finding very little research about how discovery layers affect public libraries or children.