Regarding ethical non-monogamy this film is highly overrated.
Nonmono rating: 10/4
Many mention this movie as one of the most important movies about polyamory, but if somebody wants to understand ethical non-monogamy from this film may arrive at very bad consequences. I won't recommend it as a first, introductory movie. I tell more with spoilers below.
I also have some critical notes but it may spoiler the movie. Click on the red button if you still want to read it!