Greg Elliot

A demon is released and starts wreaking havoc. He's not your standard demon, though: every time he dies, he's doubled, and then immune to that form of death.

Another entertaining Charmed tie-in novel. I'm not saying these are great literature or anything - in fact I probably won't read them again, or even keep them - but they're significantly better than many other tie-ins I've read. It's surprising.