Let's start with the positive aspects.
The cinematography and visual storytelling.
This movie has great daydream and mind reading instances where you get drawn into the world of the fml.
Where the fantasy goes crazy and where imagination takes over and sometimes crosses into the real world.

In the first half of the movie it was a true aesthetic feast and made me want to screenshot everything.
In the later half it did die down wich made the later part much more boring.

The idea of looking into someones daydreams is amazing and a truly unique concept.

Unfortunately this is one of many movies wich I would like to diagnose with: "live action syndrome".
Wich basically means: cut up story, rushed plot and inaccuracies wich are often times not avoidable.
For reference I read the first chapter of the manga wich this was based on. The manga officially ended in 2017 were as the movie already came out 2016. So I came to the logical conclusion that part of the second half of the movie was written out of thin air since the manga didn't finish at that time. (Wich also explained why it got boring)

The acting wasn't spectacular at all. The fml was a typical timid shy person.
I think the supports didn't get enough airing time, wich is unfortunate since one of the supporting actors I really enjoy watching.

My conclusion:
If for not the points above I think this is still worth the watch solely for the imaginary and visual rich instances.