It's a Steven king kind of a movie. His style is suspenseful. The monster is like his other movie called the langalier or however you spell it. Like the happening and so forth.
It does carry a message though and it is debatable which makes it an ok movie to watch and write an essay about.
Like at the beginning, we see her drawing as a painter and we see people looking down at something. In our modern world, you go to the mall and people are glued to their social media phones so maybe the message is that social media is the monster that steals our soul. We are Droid and a slave to it. Only people that are not affected by it are the people that can't see, the blind cuz the blind don't go on Facebook or do they?
The other groups of psychos are also not being affected by it but I haven't linked the connection yet.
In the book, at the last scene, the blind folks gorge their eyes out to help prevent but in the movie, no such thing.
Also the title, birdbox could have something to do with the Twitter bird logo.
I dunno, just saying