This story is more about what it means to be human and to want to live than it is about the monsters exactly. In fact they act more like a metaphor.
Some of the special effects are amazing, some are a little campy. Most monsters are well designed but a little over-the-top cartoony which I think actually works in its favor since it keeps the show from being TOO scary to the point you can't watch it without staying up all night long. The monsters are just good fun!
Main leads are all great. The two male main leads especially do a lot of heavy lifting but the WHOLE cast is great. Lots of amazing characters to root for (and root against).
Be prepared for emotions !!