**NO SPOILERS
I'm Thinking of Ending Things was a book before it was a movie, but it's also like a piece of art. I knew the movie was going to be strange and unpredictable, which is why so many people probably rated it so low. There's a deeper meaning to this movie than what it shown on the screen. Those who disliked the movie, most likely didn't think too much into the artistic perspective. It was so much nicer reading the book twice through before watching the movie, because I knew what was coming. I thought the movie would have a better way of explaining the story, but you must read the book before watching the movie.
I actually loved this film a lot. Yes, it is very confusing and 'weird', so I'd recommend reading the book first, but if not, then please watch the movie for the artistic appreciation and THINK about the deeper meaning than what is on the screen.