Having just seen both animes and acquired a taste for Boogiepop, I decided to read this spinoff / side story while waiting for my Boogiepop novels to arrive in the mail.
I didn't like it. If I used one word to describe Boogiepop Dual it would be "dull."
The story is about Boogiepop, but instead of sharing a body with Touka Miyashita as in the rest of the series, he's inhabiting the body of a boy called Takaya Akizuki. He also popped up in someone else in the past, but that's a spoiler. I didn't exactly understand the antagonist's power, and I didn't feel like re-reading it
to figure it out. Something to do with exploiting cracks in his victim's hearts, making them feel like a loser so they lash out violently. Everything turned out okay in the end, I guess.
The art has the same problem the animes had: same-face. During the climax I was trying to keep people straight by clues like "long haired girl" and "short haired girl." A few shots of Boogiepop in action were pretty cool: after all, he has that sweet cape. The rest of it was nothing to write home about. Backgrounds were standard: school roof, hospital, school nurse's office, someone's apartment. The story didn't call for anything else.
Characters were okay. Female sensei was a bit interesting. I don't remember what the antagonist's deal was and I read it last night. Boogiepop doesn't use his wires to grab things / decapitate people / tie things up, instead he shoots a bubble from his finger which makes people forget things. I think that's what it was. There are several student-teacher relationships, some sexual and one that's not sexual but a little unsettling.
It was only 2 volumes long, and I was interested enough to read the whole thing, but I'll probably forget I read it at all within a week.
If you're starving for Boogiepop and want something quick to read, you might like it. Otherwise, don't bother.