A walk through the history of digital interface design, with a focus on computer UI/UX and interactive art. Written in 2003, it feels pretty dated. The main idea is that media can be designed to be a window or a mirror.
Windows give you a direct view to information e.g. the filesystem browser on a computer. The interface should feel invisible. Mirrors are supposed to be compelling experiences that reflect the user, so for example, interactive art that displays an image of the user on a screen, collaged with other images. The interface shouldn't fade into the background. The author argues that most design should have both aspects of windows and mirrors.
One important consideration in cultural context. Someone's goal may be do design a window-like system, but without extensive UX design testing, you may just end up with something that's confusing or buggy. Designers can use cultural elements to bring context to a design, mirroring other media around us.
The author also argues that there's no single superior form of media. Instead of moving into a VR world, devices are moving into our physical world. Artists are still exploring different configurations of design.