This should've been a half hour short. The way it's told, you start suspecting the twists early on and have to sit through a very mediocre unfolding for over an hour.

Sadly, the movie was made before the advent of mass streaming.

Have yet to read the book, but since it's a short story and it doesn't have to reveal anything ahead with cheap make up, I'm guessing it presents the idea much better.

The fundamental idea is not unique or original, but fun to play with and think about. A much better but more difficult way to adapt that short story to the big screen would be to reveal the premise earlier and then let the audience enjoy and explore it in the second / third acts. Instead it's a one-act drawn-out piece with all that left to the viewer to meditate on after leaving the seat.