Augmented Reality (AR) and Virtual Reality (VR) are emerging as new media of communication and expression, but the conventions for these new media have yet to be determined. RealityMedia is a prototype to explore how AR and VR can afford existing and new forms of expression. Built on a webXR platform, RealityMedia is a browser-based immersive environment conveying the ideas presented in its counterpart printed book Reality Media (MIT Press 2021) about the history and contemporary impact of AR and VR. For this, we translate conventions of traditional media such as printed books and explore innovative VR narrative techniques. We seek to contribute to building guidelines and conventions for designing effective narrative experiences in immersive media.