I haven't seen this series yet, with the exception of the introduction and ending credits, but the animation is excellent and the atmosphere immersive; I'm anxiously anticipating the U.S. commercial release of volume one on July.06.99
It appears to be a futuristic cyberpunk story. Descriptions I've read make the storyline seem reminiscent of a William Gibson novel. The principal story is about a girl named Lain (pronounced 'lane') who begins to receive e-mail from a dead girl who says she is alive in 'the wired'.