Mystery stories are difficult to write. The fun of reading mystery stories is trying to piece together the story with the clues given. Think of mystery as a puzzle box. There has to be enough clues for the reader to participate, otherwise the reader will feel frustrated at an ending that doesn't make sense or feels cheap.
Horror stories are hard to write. The thrill of horror is reading about people being put through harsh, deadly situations and how they respond. There has to be connections between the reader and characters, and the right amount of terror where the horror becomes thrilling. If the characters don't work, then the horror becomes boring or laughable.
Another is a mystery story with horror elements (people spilling buckets of blood). This means that the mystery has to be compelling, otherwise the story has to rely on the horror elements.
Is Another a successful mystery?
NO! The mystery idea is relatable, but the mystery is poorly explained and the plot set up is poor.
Is Another a successful horror story?
No. There is plenty of death, but the boring story and cast rob the horror of any meaning or impact. The horror becomes sad and depressing rather than thrilling or thought provoking.
The only reason to watch Another is to watch how to not write a mystery. The idea of the mystery is interesting, but the cast is boring. There is little to these characters and that wipes out any tension. The horror is supposed to make the mystery more thrilling, but the lack of interesting characters means that the bloody peril means nothing. I have read that the kills are interesting, but they are boring.
I do not recommend Another to anyone. If you enjoy mystery, pass. If you are thrilled by horror, pass.
If you need to watch Another, please watch the dance scene and the pillar kill. Those are the only worthwhile part of the anime.