It's not really a film, a book, or for that matter a song. It's a radio show.
First, yes... but he penned the books, TV show and then struggled for years to make a movie work (and it doesn't) without a "big bad".
But they're all HGTTG as he didn't farm it out.
To me, it was (and is) the TV show. It was the first thing I became aware of, then the books - which start off well but get weird(er) and then nonsensical. I need to re-read them, but the latter ones where they're all strangers, a sudden change from a plane to... I forget where, there's some sandwich making, and a finality (that isn't) just make it hard work. I think that's by-design though. I was a lot younger when I last read them. I've never made it through the radio show - but I've always wanted to.