If you get past the awful opening song (it's embarrassingly bad), this show has an amazing animation style, an interesting sci-fi setting, compelling characters, and a classic plot-structure. Each episode will grip you if you can adjust to the strange but beautiful visuals. The ending is unfortunately quite bad, and ruins much of the symbolism developed throughout the rest of the series.
A surreal exploration of Japanese society. This series has elements of horror and psychological thriller, but the mood tends towards the absurd and lighthearted. I consider it a thought-provoking interpretation of mental illness and other societal phenomena in Japan.