It's a self-mocking Gainax autobiography in parody form. It's about otaku, i.e. geeks. Gainax was the ultimate studio of geeks. They sort of ruled the anime industry when Neon Genesis Evangelion came out, although that wouldn't be for another few years after this. This short series is three things at once:
1. the story of Kubou, a boy who starts out normal. After making some otaku friends, though, he gets ever more deeply involved in their lifestyle and eventually swears to become the OtaKing.
2. a thinly fictionalised history of Gainax, going through their late-1980s merchandising venture (General Products) to the anime studio they eventually became.
3. a parody documentary with live-action interviews of otaku, who I think were mostly played by Gainax-affiliated staff members. That's part of the joke. They have their faces hidden with digital mosaics, voice-changing audio and subtitles that say "NOT HIS REAL NAME". The American otaku was played by Craig York, for instance, who worked for General Products USA and apparently hadn't realised that the footage was going to be presented in such an insulting way. He got off lightly, though. The other interviewees here include someone who wears home-made glasses that unscramble the digital mosaics on hardcore pornography and someone else who might possibly be masturbating during the interview.
It's savage. This is a bracing and comedic contrast to the animated segments, which are far more positive about the otaku experience. Admittedly Kubou's story goes downhill in ep.1 from any conventional viewpoint, but he's rocket-powered in ep.2 once he starts turning his otaku-dom into business ventures.
This is cool, but there's also some history attached. This was 1991, you see, the year after the so-called "Otaku Murderer" (Tsutomu Miyazaki) went on trial. Google him. He's appalling. He caused a moral panic about otaku, taking their public image from "nerd" to "scary disturbing troglodytes who kill and rape children". He's the one who made "otaku" a dirty word for a generation... and that's the context in which Gainax released a thinly fictionalised parody of themselves called "Otaku no Video". You can't say they don't have guts, anyway.
It also has great music.
Is it funny? Well, it's no-holds barred. It doesn't really resemble anything else I can remember seeing. Its narrative doesn't go in the usual narrative directions, although admittedly it doesn't have a Gainax Ending. Your brain won't melt. Ep.2 looks as if it's achieving lift-off from reality, but in fact it's just as autobiographical as ep.1. (Well, except for the end, at least. That's obviously silly.) It's also so stuffed with anime references that I don't think it's possible to catch them all. It's both affectionately proud about otaku and lacerating about their failings, e.g. with the pornography-obsessed virgin who claims to be satisfied with 2D girls. That's since become a real-life Japanese thing, but here Gainax was pointing at it a generation before anyone else.
It's an experience. I'm glad I've seen it, anyway.