In this paper, we present CNVis, a web-based visual analytics tool for exploring data from multiple related academic conferences, mainly consisting of the papers presented at the conferences and participants who bookmark these papers. Our goal is to investigate the bookmarking relationships within a single conference and interpret various conference relationships and trends via effective visualization, comparison, and recommendation. This is achieved through the design and development of three coordinated views (the bookmark, topic, and keyword views) for user interaction and exploration. We demonstrate the effectiveness of CNVis using real-world data from three related conferences over a period of five years, followed by an ad-hoc expert evaluation of the tool. Finally, we discuss the extension of this work and the generalizability of CNVis for other applications.