Okay I think this book might be lost media at this point. I am looking for an interactive story that may have been a CYOA but might not have been that brand. It's about you getting a shrinking belt to help out a friend of yours who works at a particle accelerator to catch a potential terrorist that wants to use a belt he stole to steal secrets.
It looked incredibly old when I read it and that was like 15 years ago. I remember a few of the endings, one was you shrink into a small terrarium in the lab and are killed by an ant, another is you shrink further and get attacked by an amoeba and when you grow you are scarred and become a horror movie star. In another you are crawling in the ducts and this guy you are chasing is able to get in your ear after you get stuck and keeps singing show tunes until you give up on your mission.
The most memorable one was you go into the particle accelerator and you are fighting him on some protons and he pulls out and he threatens to reverse his atomic polarization with his belt and before you can stop him he gets hit by a proton and he turns into antimatter and explodes like a nuke destroying the whole facility.
It was a very cool adventure but I have been unable to find it for years, I remember the front cover looking very faded with a lot of reds, I think it had the particle accelerator on the front as well.