Excellent movie.
This was the first, I think, of the "theme park gone wrong" type of movie, like Jurassic Park.
It is a clever plot, well written, and expertly acted. Make no mistake, though, that this a thriller action movie, and so it's not going to be on the level of, say, Casablanca.
Yul Brynner is awesome in this movie. The movie does an excellent job at presenting the lazy, narcissistic, decadent lifestyle that the visitors to the park (and the world in general, I presume) had gone down to. So you don't feel that bad when "karma" rears its head.
An excellent movie. If it comes on tv or you can stream it, watch it. You won't regret it.