u/Alarmed_Ferret_641

Sometime around 2000 I remember reading a mystery novel. The novel was about a girl investigating the disappearance of a high school classmate. It involved a cult which turned out to be led by the girl's chemistry teacher. What made this book a bit unusual is that it was published with the final chapters in uncut pages--that is, you'd read almost to the end and then you'd need to use scissors to cut the final chapter open. It was a gimmick intended to keep you from turning straight to the solution to the mystery, I guess.

I think (but am not sure) this was part of a series which presumably used the same gimmick. Does this ring a bell for anyone, or does anyone have any ideas how I might search for this? My usual Google fu isn't working.