This is a really distinct and kind of crazy film that pairs a plot that could be in a horror film with a bit of a retelling of the story of Sisyphus. It is also, perhaps, the most incredible use of sand in a movie in film history.
Very mild spoilers
Despite some plot similarities with other films, this is an utterly unique film, like nothing I’ve ever seen. (And, I suspect, like nothing anyone in the English-speaking world had ever seen in a film in the mid ’60s.) The film combines the “stranger trapped in a strange place/house” plot with an allegory similar to that of the story of Sisyphus. The allegory is much more interesting as a story in a story like this because, as others have noted, there’s enough going on (and the characters are literally drowning in the absurdity of the situation and life itself).
Sand has never been more terrifying in a film. Sure, there are quicksand pits in other movies but I’ve never seen anything like the all-out assault of sand on hope that you see in this film. There’s just no escaping it and it’s menacing in a way that nature rarely is on film.
The score is incredible and might be one of the landmark scores in film history. I don’t know exactly when atonal music and horror first became associated in film but this film is certainly one of the earlier ones. There are moments in earlier films that make the association for sure, but this score is aggressively out there compared to western music (film music and concert music) and the reception this film received likely help make the score more influential than if the film hadn’t been such a big deal. (Takemitsu had been doing scores for 8 years so it’s unlikely this is the first score he made like this.)
The film (or its source novel) appear to have inspired numerous other stories, such as The Wicker Man, The Collector, Misery and stories of that ilk. None of them are direct inspirations, they just have thematic similarities to the plot (not to the philosophical themes). And unlike some of the books and films it (or its source novel) inspired, this has the courage of its convictions.
I have only one quibble, and that is I see a fairly obvious way out that our hero never tries. It reminds me a little bit of how in The Maze Runner they have a fucking forest and nobody thinks about building a ladder. I’m very sorry to mention The Maze Runner in the presence of this great movie, but there we are. Anyway, it’s a bit of a problem though I’m very willing to overlook it given how great the film is as a whole.