Phenomeno, after you read the synopsis, maybe some of you will think that its something so-so just like another mediocre horror story out there, and then reluctant to read it, but wait a minute, I'll try to explain what makes Phenomeno special. (By the way I'm not a horror fans)
Though I've watched and read many type of horror works before, I still find Phenomeno's story so interesting to follow, the whole forum thing is a plus for the story and it makes the story feels unique. The story is told from the perspective of Yamada the main character. You'll find the main characters explore
various horror places out of curiosity and so on, so the story is quite simple and the plot detail isn't too deep & complex, so you'll find it easy to understand. The pacing is a bit fast in my opinion, but in a good way. I believe this kind of pacing in a horror story could keep the reader to stay tuned to the story. About the spookiness level of the story, if I put it into number then it'd be hmm..7 out of 10, that's my opinion, to know it for sure of course you'll have to try it yourself, this kind of judgement could highly differ between people after all.
Next is the characters, which I think is the main charm of this novel. The main character, Mitsurugi Yoishi, she is an eccentric, mysterious, & mysteriously beautiful teenage girl whose eccentricity & mysterious behavior could makes you curious and want to know more about her. That's why her character could makes you want to immerse yourself deeper into the novel and that's also why she could transforms the story into something more interesting than it would be. The other main character, Yamada, he's a main character you'd expect from this kind of horror story, I think his reactions & attitude is quite normal, and he is quite a coward for someone who loves occult thing. He is your typical 18 years old boy with a good morality, Yamada is some kind of "stabilizer" for Yoishi's eccentric attitude. The perpetual interaction between Yoishi and Yamada could make their character developed considering their opposite personality, I've seen the omen. As for the supporting characters, I couldn't say much about them, but they're definitely not bland and have some potential to be developed.
The Art, it's beautifully made by Yoshitoshi ABe, the art is beautiful & has a nice texture which fit for the atmosphere of this novel, you wouldn't be disappointed by ABe's works. By the way ABe is the one responsible for Serial Experiment Lain & Texhnolyze's art, both of them is dark anime. He always did an excellent job indeed.
So, when I found such wonderful character combined with simple yet interesting story in this novel, that's when I found the enjoyment, a big enjoyment. In the end, Phenomeno always makes me curious about the progress of the story.
By the way I read the first 2 chapter through the visual novel adaptation, it's well-made by Nitro+ and free to download, it has an excellent sound, it makes the creepy atmosphere far more stronger. So I highly recommend you to start with the visual novel adaptation to build the atmosphere.