I'll give it a rating of 7 because of the interesting first season (not including season 2 and especially not season 3) and the good special effects. Otherwise, I would give it a rating of 5 for the storyline.
Season 1 of this series is quite similar to the comic, with a few new characters and changes in character details, but it's still interesting. The series doesn't explain in depth how human desires turn people into monsters, but it's still worth watching.
Season 2 starts off well but quickly gets filled with unnecessary scenes and characters. These new characters don't add much to the story and take away from the interesting development of the existing ones.
However, Season 3 is where things go really wrong. Like many Korean sci-fi and mystery dramas, it fails to wrap up the story in a clear, logical way. The Main enemy monster died in unrealistic and silly ways. If it could be defeated so easily, why wasn't it done sooner? The idea of new Neo-humans is also confusing and not well explained.
The main theme of "Sweet Home" becomes unclear. The only somewhat developed relationship is between Cha and Eun Lee. Many characters from Season 1, whose relationships were built up nicely, are ignored or poorly developed in season 2 and 3, favor of new, less interesting characters with shallow backstories.
In summary, while the first season is promising, the next seasons, especially Season 3, fall short and end up ruining the series.
