Considering the lack of systematic reviews on e-government research, this study includes research categories, spatial structure, research paradigms and noteworthy future topics in the domain of e-government. We collect 142 keywords from 2646 papers published in the Web of Science from 2000 to 2019 as the study object. Then, we identify four research categories: (1) technology and modelling in e-government, (2) drivers of e-government development, (3) public management and (4) governmental management. From public and government perspectives, we outline the spatial structure which includes theories and practices research and conclude four research paradigms: (1) theoretical modelling and application, (2) e-government development, (3) status of public management and (4) status of governmental management. Finally, we develop a 3D spatial map to analyse noteworthy topics and explore the well-studied themes: government-to-citizen, government-to-government and government-to-business, and the under-studied themes: government-to-civil society organisations and citizens-to-citizens, which helps scholars research e-government roundly.