"Serial Experiments Lain" is a story about a schoolgirl who discovers Cyberspace, is then drawn into a series of mysterious incidents, and in the end saves the real world from dissolving into the net.
It is also an outstanding anime even among the ranks of Cyberpunk classics.
The series features a distinctive style that combines very calm, at times almost motionless, animation, set in bland but high-contrast colors, assembled in imagery that is smoothly rendered and would be photorealistic would it not be so distant and lifeless. From the very first minute it is clear that this "real world" is a very strange one, because while it looks like something we know, we feel that the camera is inherently helpless trying to capture the actual developments going on beneath the surface of the objects that are filmed. The camera cannot do better, obviously, and we see electric wiring and telephone cables, hear their monotone humming, see computer machinery filling every inch of Lain's room, hear their harddisks running.
So while we see technology through its outward appearance, that all this machinery represents a consciousness of some sort doesn't seem too far off, and some entity hidden in the net is obviously pulling the strings behind the events Lain experiences. This is different compared to other Cyberpunk anime, where it is at some point explained to the viewer that something, or somebody, has awoken in the net: In "Serial Experiments Lain" this explanation is unnecessary, we feel it from the beginning.
All of this seems strangely attractive, especially for the sort of net-dwellers that we are, although it is also creepy.
The series progresses as Lain finds out more and more about the tremendous power that she has -- which, in a not very easy process, she learns to use -- and in the end does what has to be done, to keep the worlds separate.