This is one of my all time favorite movies. But... and this is a major but... at least part of my appreciation stems from the fact that I watched it several times and that I've also read the book (by Paul Bowles) two or three times. So both works of art (since the book is most definitely a work of great art) tend to blend together in my mind.
I started by watching the movie though, without any previous knowledge on the novel, nor on Paul Bowles. I was impressed by the powerful imagery (theater! not dvd) and chilled by psychological the harshness of the plot. I was charmed the first time I saw the film but I fell in love when I saw it a second time, which was after I'd read the novel. Maybe this means that the film doesn't 'make it on its own', but to me that's not a problem. And if you are, like me, gripped by the movie I can really recommend the novel for more 'in depth' .
Some people here seem to think that there's no plot or just a very thin one. I disagree. It's not directly on the surface though. You'll have to concentrate and pay attention to dig it up. If you don't like that or feel that a movie should just willingly present itself to you, than this is not your movie.